There are few films, outside of the horror genre, where a character’s exterior so aptly mirrors the evil brutality within as Johnny Depp’s James “Whitey” Bulger in the gripping and brutal crime saga “Black Mass.” With dead, cold-blue eyes set against a cadaver of ashen, white skin, Bulger is more reptile than human, a man with neither soul nor conscience. That Bulger really exists — he ruled the Boston underworld as the head of the Irish-American Winter Hill Gang in the ’80s and early ’90s — which makes it all the more creepy.