Ahhhh I love when people ask me this. I feel like you're the same person who asked me what makes me think Erik is a bottom, but I could be wrong. *puts on professional glasses once again* Please be prepared for the following explanation.
To start this answer I’ll put it like this: T'Challa is not afraid to be a real man. Not to take anything away from Erik, but T'Challa is not afraid to express his emotions and he treats everyone with respect unless you’ve crossed him. Also he's the flipping Black Panther and king of an entire nation, a rich, technologically advanced nation at that. To me that's automatically right there a dominant presence.
However, if you're talking T'Cherik wise, here is some evidence.
First, take for instance when Erik first walks into the throne room and there's T'Challa sitting on the throne looking like the king he is.
Can you not feel the dominating presence here? His eyes, his overall facial expression, his posture relating to the way he sits on the throne. T’Challa is letting everyone in that room, including Erik know that he is the king, you will respect it, and no one is going to take that away from him. At least that’s what he thought at the time. But I will say I’m positive that when Erik first walked in and saw the way T’Challa controlled the room at the time, he tried not to show it but his knees probably went weak and he probably had a moment where he thought about getting down on them in front of everyone. Basically, T'Challa is radiating BDE as always.
Next scene in the throne room when T’Challa gets up into Erik’s face.
T’Challa is trying to show that he can be intimidating yet teasing Erik with the power he has. Still having ingested the heart-shaped herb, his strong senses could still figure out that Erik has a weakness: T'Challa. Look at how Erik looks at T’Challa up and down as he backs up. And as I mentioned before Erik’s lips do fall open as if he was expecting a kiss from T’Challa (which is what he wanted). Anyway, T’Challa is definitely sensing out his potential lover to see if Erik is the one.
As you can see here T’Challa’s still checking out Erik before and after he strips his shirt. Now, do you see the look in T’Challa’s eyes? He’s mentally saying Erik may be crazy, but he could be his consort and rule by his side instead of taking his position. And his thoughts are proven through his actions when he tries to get Erik not to fight him and when they are fighting he tries to get Erik to yield. T’Challa being the sympathetic king that he is probably wanted to go sit Erik down, talk it out, and possibly do the do. However, did Erik allow that? Nope.
Skip to when T’Challa comes back from the grave:
T’Challa’s standing on top of one of Erik’s ships that he knocked down himself, fire surrounding him as he’s dressed as Black Panther. Again, T’Challa is letting everyone know loud and clear for real this time that he is the true king and Black Panther. This goes back to the whole dominant presence. Do you remember the way Erik looked when he came back? I couldn’t find the gif of it but he looked shook! I mean he was shook at how hot T’Challa looked when he unmasked himself being that that’s the first time he's seen T'Challa in the suit. However, once again he couldn’t show that he would bottom for T’Challa 24/7.
Also this scene right here:
The way T’Challa called out Erik’s government name. He's still letting Erik know T’Challa has the true authority around here and he will have that same authority over Erik, specifically in the bedroom. But to call out Erik’s true name, it shows that he respects Erik's true roots and he still wants to give him the chance to be his, that they can work this out. But does Erik allow that? Nope. I say again he doesn’t want to show he’s a bottom in front of everyone so instead he chooses to fight his potential lover.
Lastly, the sunset scene:
The whole sunset scene was T’Cherik gold and no one can convince me anything else. Anyway, you see despite having to fight Erik in the end because he still wants him by his side, he fulfills his lifetime wish of seeing a Wakandan sunset. And you see while there he offers to heal Erik. Since T’Challa is technically king again he has the power to heal him and by this time T’Challa has figured out his true feelings for Erik. Do you see the way they look into each other’s eyes? T’Challa has kind of a strain in his face that says ‘you better say yes’ meanwhile you can see Erik wants to take him up on the offer and be by his side too. Does he though? Nope, because once again Erik can’t express his true feelings and knowing he’s going to bottom so he feels the only way out is to kill himself.
To sum this up, I think T’Challa is a top because he has a dominant presence to him that’s been there since the sixties and in the MCU since Captain America: Civil War. Also, I said at the beginning too that what makes him a top is that he’s a real man because of those attributes. They have been described throughout this essay to answer your question on why I think T’Challa is a top.
I hope I did answer your question as detailed as I could. And thank you for asking.
For the anon who asked this I’m sorry I couldn’t answer it in the correct ask format, but I hope you see it and like my answer for you.
P.S. Erik’s behind is fat, T’Challa’s ding dong is big and that’s another reason right there. *shrugs*
