This is one of best movies in DCAU because of how well it is written and how close it stays to the source material while putting an original touch on it.
Although development hell seems to have claimed the long-hyped Gambit film (featuring Channing Tatum as the titular mutant hero), we now know one villain who was set to appear. Mister Sinister was set up in the end credits of X-Men: Apocalypse.