I'm convinced that if circumstances had been different, they would've been friends, or at least gotten along in some fashion. Megatron and his abuse/Starscream's Stockholm syndrome was all that ruined their chance at having a positive relationship, istg.
If Megatron hadn't noticed Starscream was afraid of predacons and put them together specifically to fuck with Starscream, or if Shockwave hadn't threatened Starscream's safety by potentially replacing him and rendering him 'useless' in Megatron's eyes? If Predaking had realized the position that Starscream was in???
Megatron would've literally murdered Starscream if he didn't prove useful to him; he literally said that to Starscream's face and tried to kill him multiple times already by that point. Starscream tried to live by himself, but had nowhere to go and no allies, struggled the entire time, and only survived by the skin of his teeth and extreme good luck.
Starscream wasn't being a hard-ass to Predaking out of cruelty; it was pure desperation. Desperation to tame what Starscream and the other Decepticons believed was a dangerous animal that - according to historical record - regularly ate Cybertronians. It'd be the equivalent of an army general ordering someone to tame a man-eating grizzly bear under threat of being executed if they failed.
Starscream bringing up the idea of terminating Project Predacon is - context in mind - obviously also an attempt to prove useful and keep his standing from being usurped by Shockwave. Most of Starscream's motives behind 90% of the stuff he does during that point in the story is trying to convince Megatron he's still useful so Megatron doesn't fucking murder him.
Starscream shooting Predaking in the back when he fought Megatron is also another act of desperation, coupled with a 'rock in a hard place' scenario. Because while on the surface, it seems like he could've easily benefitted no matter who won, allow me to point something out:
Megatron, Starscream's abuser, has died multiple times already by that point, but has come back each time and beaten Starscream nearly to death every time he's returned. Ultimately, Starscream choosing fawn and helping Megatron makes more sense when you consider that regardless of what happened, if Starscream didn't help, Megatron probably would've hurt him, or killed him; if he lost, Megatron could just return to life and seek vengeance on Starscream, and if he won, Megatron would've known Starscream did nothing and probably would've beaten him for doing nothing.
Ultimately, what I'm saying is, if Starscream and Predaking had the time, conversations, and neutral environments to do so, I'm convinced they would've at least been friends. I mean, ffs, Starscream ended up having that time, conversations, and neutral environment with Shockwave in the TFP movie, and THEY somehow ended up becoming friends.
Poor Starscream. First, he's born into Quintesson slavery, watched Megatron commit genocide against his entire race, had to deal with Megatron's abuse for years, watched the last seekers (to his knowledge) die (And no, the vehicon seekers don't count, they're canonically considered their own thing), then he tried to escape his abuser and got organ harvested, almost starved to death, had to murder a clone of himself, then all the shit involving the Stockholm syndrome and Predacons?!
Also, just now realized after typing that out: Megatron canonically committed genocide against the Predacons, then did so to the seekers, then did so to the predacons for a second time (And a third time, if you count when he brought them back as zombiecons). Jesus, reverend-
Predaking and Starscream have a common enemy for a common reason, and are both intelligent, well-mannered warriors! They have a lot more in common than it seems, and the fact they're both - to their knowledge - the last of their kinds??? Come on now! That could've been such an interesting dynamic!