T'Challa: Two people in a room can get more done than a hundred.
King T'Chaka: Unless you need to move a piano.
T'Challa: In my culture, death is not the end. It's more of a stepping off point. You reach out with both hands and Bast and Sekhmet, they lead you into the green veld where... you can run forever.
Natasha Romanoff: That sounds very peaceful.
T'Challa: My father thought so. I am not my father.
Natasha Romanoff: T'Challa, Task Force will decide who brings in Barnes.
T'Challa: Don't bother, Ms. Romanoff. I'll kill him myself.
Sam Wilson: So you like cats?
Steve Rogers: Sam...
Sam Wilson: What? Dude shows up dressed like a cat and you don't wanna know more?
Steve Rogers: Your suit. It's vibranium?
T'Challa: The Black Panther has been the protector of Wakanda for generations. A mantle passed from warrior to warrior. And now because your friend murdered my father, I also wear the mantle of king. So I ask you, as both warrior and king, how long do you think you can keep your friend safe from me? (00:55:00)
Chosen answer: Because the U.N. has been preparing to pass the Sokovia Accords and they want to oversee the Avengers. A week earlier, the Avengers would not have had to seek permission to find the other Winter Soldiers (or wait while the oversight committee makes a decision). As a result of the U.N. Sanctions, Captain America and Sam Wilson have to go rogue in order to find the other soldiers. (Their actions of going rogue result in Iron Man and his team in hunting the rogue Avengers down, creating a "civil war").
Bishop73