Pretty simple, just do as the achievement says, beat every villain with Batman, even if they aren't in his rogue gallery like Doomsday.
Campaign villains beat while playing as Batman DOES count, afterwards I only had to beat a few more to get the achievement. If you're unsure, just keep track during the story mode, but you will definitely have to beat at least Ares, Grundy, Doomsday, Killer Frost, Sinestro, Black Adam and Harley separately.
All you have to do for the extras is load up a second controller in Multiplayer->Versus and beat the crap out of the 2nd player. You can also work on your Around the World and super moves achievement while doing this, which is what I recommend to save time.
In story mode u battle deathstroke, bane, lex, joker, catwoman. That leave harley, grundy, ares, killer frost, doomsday, sinestro, and black adam that u have to battle.
Posted by OneManMafia86 on 19 Apr 13 06:25:03