Doctor Manhattan
Who is he? Formerly a nuclear physicist, John Osterman was disintegrated by an Intrinsic Field Subtractor (ouch) and redeveloped himself over the next handful of months. With godlike powers ranging from omnipotence and complete intelligence to being able to blast anyone to pieces, he’s the most powerful character in the universe, but also the most emotionally unstable, unable to keep relationships and eventually just fleeing to space so he can “create life” in another galaxy.
Why include him? Even though the Watchmen comic doesn’t really specify his powerset as magic, his powers pretty much are that to some extent. Like with Zatanna and our suggestion of Doctor Fate, Injustice 2 is said to have more magic characters this time around, and he’s as magical as that universe can get. A naked blue man tends to do that.