The Butterfly Effect (2004)

Evan changes his childhood to produce hand scars, which his prison cellmate sees appearing in the present. Elsewhere, altered history rewrites whole lives; here the scene needs both the unchanged cellmate and a fresh, visible miracle. It is a conspicuous exception to its own cause-and-effect game. The attraction survives in the unnerving idea that improving one friend's life can wreck another's, though the film's abuse and violence make this a bruising watch.