Killer Mike is proud of Tity Boi (2 Chainz) + Future because of their persistence and individuality.
Mike states that Tity Boi was in a group, Playaz Circle, for years before he blew up. Even though he was overlooked for such a long time, Tity Boi never gave up and Mike respects that about him.
The fact that he never gave up is something that Mike relates to and understands, so he has nothing but love for 2 Chainz f.k.a Tity Boi.
As for Future, it's a no brainer, he's part of the Dungeon Family and he did his thing by finding his own lane. In summary, Future's "melodies are dope" according to Killer Mike.
Watch the clip here: