At the recently held ELEAGUE Injustice 2 World Championships, NetherRealm Studios revealed the other characters that would join the Atom in the Fighter Pack 3 DLC.
I'll let the video reveal do the talking:
Yes, in addition to the Enchantress (which you might find familiar from last year's Suicide Squad movie), the Teenage Mutant Ninja Turtles - Michelangelo, Leonardo, Donatello and Raphael, will be joining the roster of Injustice 2 in this upcoming Fighter Pack.
We are yet to find out whether the turtles will be considered as one collective character or if they will form four separate characters but nonetheless it is an interesting guest appearance to the game's roster.
A release date for the fighter pack was not announced during the event buy Polygon states that the Atom will be made available through Early Access on December 12. That puts the release for Fighter Pack 3 potentially after that date.