Ben Affleck  showed off his huge back tattoo during a training session for a movie, despite the fact he once claimed it was not real.  The Justice League  actor, 45, exposed the permanent ink while training alongside his Triple Frontier  costars, Charlie Hunnam , Garrett Hedlund  and Oscar Isaac , in Hawaii on Thursday, March 15, as they prepared for the movie while working out on the beach.  The massive tattoo, featuring a colorful phoenix spreading its wings, made its first appearance  in December 2015, when Affleck was working on the set of Live by Night.  The Batman v Superman: Dawn of Justice  star reportedly got the tattoo, which symbolizes rebirth, after then-wife Jennifer Garner  filed for divorce after 10 years of marriage. The pair share children  Violet , 12, Seraphina , 9, and Samuel , 6.  While an insider told Us Weekly  at the time that Affleck had gotten the tatt at home, he later denied that it was permanent , explaining the tattoo of the my...