Injustice 2 showed off DLC pack 3. No people had there predictions but no one say who would be the guest in this pack. I can tell as The Teenage Mutant Ninja Turtles is the biggest surprise we have. So to recap we have The Atom, Enchantress and The Teenage Mutant Ninja Turtles.
If you missed will post the teaser as well as Max reaction to it below. But also Max brings up a good point do get to switch between the brothers thanks to gear you have to get or do you control all 4 in games summon one at a time through gameplay. We will have to wait for more details. They look just like they did in the original live action movies. 
Article:https://www.eventhubs.com/news/2017/nov/10/ninja-turtles-and-enchantress-join-atom-fighter-pack-3/
As always thank you for reading.
