Dolph Lundgren has spoken about the fact that his character’s life basically fell apart following the loss to Rocky, so while Adonis Creed may feel like he has something he needs to prove, he’s not the only one.
Of course, every villain is the hero of their own story, and while we might look at Victor and Ivan Drago as the bad guys, it doesn’t appear they see things that way.
We know from the trailers that Victor Drago is the one that issues the challenge to Adonis, which indicates that Drago feels he has some unfinished business as well, with the protege of the man who defeated his father.