It depends on the game... VF player take the down attack post KO as an insult, but if they're still standing, I combo or do a crazy dance/stairstepping. Same with Tekken, I combo or do some sort of dance.
In KOFMI I think I just did Alba's super or his qcb+A which sent the guy flying anyway...
Real talk, MI's Seth should've been in the 2D KOFs... I think that version played so much better than the original...