This requires you to have already beat Story Mode because you'll need a win with Brainiac. The quickest way is to grab a second controller and work your way through each character in Versus. Before anything though, go to Options and change it to one round per match to speed things up.
The characters you need wins with are on the right side of the Player Select menu. These are Catwoman
, Wonder Woman
, Black Adam
, Captain Cold
, Gorilla Grodd
, Poison Ivy
. Wonder Woman, Black Adam and Superman are optionally playable during Story Mode so there's a chance you will have already made progress with this achievement if you did the story before anything.
In Versus, choose each character with your main controller and spam
. Stand still and wait for the opponent to ricochet back to your feet and just repeat the combo. Each match will take you around 15 seconds. You'll get most of these going for the 28 character-specific win achievements anyway. Brainiac will be the only thing holding you back at first.
EDIT: Added Catwoman