Bucky is an Avenger, Steve and Sam's best friend. But he's got a secret, he's in live with Y/N Stark.. Y/N is Tony's oldest son. But Y/N is the villain.

the Avengers managed to get Y/N into a cell, with bucky there So bucky asks

Bucky: Why'd you become the villain...?

Y/N:Says with tears in his eyes I learned two things that day.. 1.I was never gonna let anyone see that they got to me. 2.if the worlds gonna see a shifty and untrustworthy person helping, then there is no point..