On Nico's Ability to Defend Himself
An often-overlooked aspect of Nico's death scene in TFATWS is that there was literally nothing preventing him from thwarting John's attempt to kill him, and keeping it from being a death scene; he just didn't so that there would be a reason for the Captain America title to be stripped from John and given back to Sam. I feel like a major reason why a lot of people don't pick up on this fact, and instead perceive Nico to be defenseless (aside, of course, from the shamelessly manipulative framing) is that in the Siberia incident, the incident Nico's death scene is frequently compared to, Tony, after he lost the upper hand, didn't really get a chance to do much before Steve disabled his suit. It thus didn't stick out too badly when Nico also didn't do much before John attacked him with the shield, even though there was a lot more he could have done. Therefore, let's examine the two situations to see how they are different.
This is how the shield incident played out in Siberia. Near the end of the battle, Tony had managed to gain the upper hand and inflict serious damage on Steve. After Steve refused to stop defending Bucky, Tony prepared to straight up blow Steve out of the bunker and down the mountain: but right before he got the repulsor shot off, Bucky grabbed his leg. Irritated, Tony turned and kicked Bucky in the head with his metal boot. Then, before Tony had the chance to do anything else, Steve grabbed Tony and hoisted him into the air; Tony tried to use the jet packs on his boots to get out of the situation, but too much damage had been inflicted on them at that point for them to be of use, and Steve threw him to the ground. Steve then immediately rushed on top of Tony and punched his face mask three times out of sheer fury, after which he broke the helmet by hitting it twice more with his shield and then tore it off. He subsequently raised the shield, which caused Tony to frantically raise his arms to cover his face, and this allowed Steve to have a clear shot at the arc reactor, which he brought his shield down on and broke.
Now, considering how thoroughly biased Civil War is against Steve, and how much it sought to act like he was the one in the wrong—even though the entire Siberia fight was literally just Tony having a temper tantrum and Steve and Bucky trying to survive it—the creative team certainly wouldn't have minded if Tony had cried out in fear like Nico did, as it would be quite useful for the propaganda efforts. Therefore, there is clearly some reason why he didn't.
And it appears that there are two main reasons for this. The first reason seems to be that everything simply happened too fast. Indeed, the entire incident, from Tony preparing to shoot Steve to Steve disabling the arc reactor, took place in the span of about fifteen seconds. And Tony totally wasn't expecting Steve to grab him; presumably, he assumed that Steve was injured enough that taking his attention off him for a few seconds in order to kick his friend in the head wasn't a big deal. He underestimated the strength that poured into Steve's limbs when he saw Tony so callously abusing Bucky, as well as the fact that Steve is a supersoldier, so he can move really fast when he wants to.
So there was the element of surprise, and there was also the fact that Tony probably would have been a little stunned, both from the impact of being thrown to the ground, and from being hit in the head multiple times. It must, of course, be remembered that Tony was wearing a full-body metal suit, so no actual harm was inflicted upon him, but Steve is a supersoldier, so even with the layer of protection the impacts would certainly have been felt. These factors combined to produce the effect that, when Steve raised his shield, rather than take the time to yell anything, Tony simply prepared himself to face what was about to happen, which he thought would be Steve attempting to end him. But fortunately for him, he was wrong. Steve wasn't trying to kill Tony; Bucky was still alive, so Steve was able to contain his fury enough to refrain from a killing blow, and he hit the arc reactor instead.
Now, let's look at how Nico's death scene played out. After John pursued Nico for a bit, and managed to fend off a concrete trash can that Nico threw at him, he was able to hit Nico with the shield as Nico ran into a square. This forced Nico to stop to keep his balance, which allowed John to hit him again, and this finally knocked him over. Nico then tried to get back up twice; the first time John hit him with the shield again to keep him down, and the second time he put his foot on Nico's chest to pin him to the ground and stop his escape attempts. Then, since he couldn't try to get away anymore, Nico waved his hands and nervously insisted, "It wasn't me." He said this because, given the role he played in Lemar's death, he was well aware of why John might be mad at him specifically, for more than just being a friend of Karli. John, for his part, had been preparing to interrogate Nico about Karli's whereabouts, but this clear falsehood evidently filled him with rage, and he raised his shield in a fury. Rather than make an effort to block the imminent attack, Nico simply repeated, louder, "It wasn't me!" even though it was clear that John was not about to accept his garbage. And then, of course, since Nico wasn't about to actually do anything, the beating with the shield commenced.
Nico just lay there and was obediently killed, even though there was literally nothing stopping him from simply catching the shield and keeping it off his chest. His arms and hands were not at all restrained—indeed, he was waving them around—and unlike John, who had acquired a gash on his head, Nico was completely uninjured, so there wouldn't have been any pain distracting him either. And as we saw earlier, Nico is just as strong as John—he was able to restrain John so effectively that Karli would have been able to easily stab John if Lemar hadn't stopped her—and his evident fear would likely have given him enough strength to cancel out John's rage. So he would certainly have been able to keep the shield off his chest until Sam and Bucky, who appeared shortly afterwards, could save him if they wanted to.
Indeed, Nico didn't save himself even though, as evidenced by the fact that he did actually have a chance to cry out, he was dealing with a much less challenging situation than Tony was. For one thing, John bringing down the shield on Nico's chest was not at all a surprise. After John had pinned Nico to the ground, Nico had time to say, "It wasn't me" before John made any sort of move: and after John registered what Nico had said, he shifted his shield, which had been on his arm, into a two-handed grip, and then raised it. Nico clearly saw this coming; indeed, this is what caused him to shout "It wasn't me" a second time. And John's intentions at that point were obvious, so it's not like what happened with Tony where Tony thought that Steve was going to do one thing but he did another; it was pretty clear where John's shield was going, and this would have been plenty apparent to Nico since terror tends to make time slow down. So he had ample time to catch it.
Additionally, Nico would not have been stunned in the way that Tony was. Tony was slammed to the ground and then received five forceful rapid-fire close-range blows to the head, which is several hard impacts in a short span of time. Nico, by contrast, was hit once with the shield, then was knocked by John to the ground. This was a much shorter distance to fall than the overhead bench-press position that Tony was thrown from, and there were even stairs to break Nico's fall. Thereafter, Nico was hit with the shield again—and he hadn't gotten very far up, so he didn't fall very far back down—and then John thwarted Nico's final attempt to get up by pushing him down with his foot. In addition to the fact that the push was much gentler than getting hit with the shield again would have been, as before Nico hadn't gotten very far up, so he wouldn't have hit the ground that hard.
Therefore, in contrast to Tony, who received six sharp blows pretty much back to back, Nico received three fairly spread out blows—after the first hit with the shield, John had to close the distance between them and wind up again before hitting him a second time to knock him over, and then Nico fell to the ground and started to get back up before he was hit a third time—as well as a kind of shove. Nico thus did not receive nearly as harsh a pummeling as Tony did. And on top of that, he is a supersoldier: so even if his treatment had been rougher, Nico would have a much higher tolerance for pummeling than normal human Tony would.
Hence, Nico would not only have had plenty of time to see what John was doing, but he also would not have had to contend with the disorientation that Tony experienced. There is no excuse for why his only reaction to John's attack was yelling.
And here's what makes the fact that Nico didn't try to defend himself even more ridiculous. Even though Steve's attack was much more rapid, forceful, and unpredictable than John's was, Tony STILL did the logical thing and was ready to try to catch Steve's shield. Indeed, you can actually see a bit of strategy in his response to Steve raising the shield. Tony knew he wasn't strong enough to entirely keep the shield off his face since his suit was failing, so rather than try to stop it from hitting him, he was instead planning to try to grab the shield during its descent in order to slow it down and cushion the blow. As Steve brings the shield down, you can even see Tony open his fingers as he expects to encounter the shield. Nico did not do anything of the sort, he just aimlessly shouted as he passively lay there and waited for John to kill him. But come on! If Tony, who was just a normal human encased in a suit of rapidly failing metal, and who had been completely taken by surprise with a harsh walloping, could make an attempt to stop Steve from killing him (even though, as it turned out, he didn't need to), then Nico, who was a supersoldier, and who had received far less of a thrashing, could definitely have tried (and succeeded) to stop John from killing him. Especially since, unlike Tony, he actually would have been able to completely stop the shield from hitting him.
There is another difference between the two situations that is very interesting, however. Tony, for his part, was well aware that he was acting dishonorably. For instance, a little after Tony began his assault, when Bucky was trying to run away and Tony was intent on pursuit, Steve stood in front of him and said, "It wasn't him, Tony. Hydra had control of his mind." But Tony already knew this, so he simply responded "Move," in a way that clearly indicated that he didn't care and didn't want to hear it. And a short time later, when Tony prevented Bucky from escaping, Steve tried again to get through to him and said, "This isn't gonna change what happened," but Tony replied, "I don't care, he killed my mom." Tony knew that Bucky wasn't to blame for his parents' deaths, and that killing him would not help anything: but since he was angry with Steve for refusing to accept the Accords and all their rights-violations, he saw the revelation as an excuse to attack both Bucky because he knew it would hurt Steve, and Steve himself because Tony knew that Steve would not just stand by while Bucky was being assaulted. He ignored Steve's attempts to reason with him because he figured that he had enough power to be able to do whatever he wanted, and he also correctly guessed that Steve and Bucky would continuously hold back against him, even though they shouldn't have. And because of these things, before Bucky's intervention, Tony had been about to do something that could have quite possibly ended Steve's life. So when Steve regained the upper hand and Tony was at his mercy, Tony was aware that he had no right to ask Steve to spare him, because when he had been in Steve's position, he had been ready to potentially end Steve's life without a second thought. Therefore, he said nothing; his only response was to see if he had enough strength left to hold off Steve.
So Tony, in the face of Steve's attack, didn't yell anything because he knew that what he had done was indefensible: and it is due in part to this modicum of contrition that Steve was able to contain his rage enough to spare him. Nico, meanwhile, had been doing something similarly heinous. He had been actively engaged in trying to kill John because John was Captain America, and when Lemar frustrated the attempt on John's life, Nico was also the reason why John was unable to protect Lemar from Karli's subsequent death-blow. And just like Tony, Nico had been relying on his strength to protect him from repercussions. So what he had done was just as indefensible as what Tony did: but instead of taking the smallest bit of ownership of this, he tried to completely absolve himself of responsibility for what had happened, and this resulted in his downfall. For while John had clearly been intending to just interrogate Nico, the fact that the person who had held him helpless while his best friend was murdered was trying to act like he was not at all responsible for what had happened caused him to lose it, and this resulted in the shield incident. Now, Nico definitely should have made it clear that he was surrendering if he intended to, and even apologized if he genuinely regretted what had happened to Lemar: and again, when the attack did happen he could have easily fended it off. But if he had simply recognized the fact that he was not worthy of John's mercy since he had not been prepared to show mercy to John, and remained silent like Tony did, the shield-attack would never have happened in the first place.
But in any case, as mentioned above, Nico didn't try to defend himself because John needed to kill him, so that the show would have an excuse to take the Captain America mantle from John and give it back to Sam without it seeming too dubious. (Though considering that the incident ended up resulting in Sam and Bucky attacking John for the shield a very short time after he literally lost his best friend, the show completely failed at that.) Not to mention, if Nico had put up a fight, this would have highlighted how much he was still capable of threatening John, and put lie to the show's attempt to act like he was helpless. Particularly since, again, if he had tried to save himself there is no reason why he would not have been successful.
Now, it is important to also remember that Nico was definitely not surrendering, the other widespread misconception about his death scene. He kept trying to fight John until he literally couldn't—he threw a concrete trash can at John while he was running away, and tried to get back up twice after John initially knocked him over, which is not something someone who wanted to surrender would do—and then after John had him pinned, all he did was try to disingenuously absolve himself of responsibility for Lemar's death, rather than trying to apologize or making it clear that he was surrendering. But on top of the fact that Nico wasn't trying to surrender, and refused to own up to what he had done, he was perfectly capable of surviving John's attack when it happened. These things make his death scene, as well as the subsequent reaction to it, completely ridiculous and utterly nonsensical.
