1x11 - Highlander: The Animated Series

Ramirez shows Quentin how the Great Catastohphe came to pass. In doing so, Quentin decides the horrible knowledge of nuclear weapons is something he can not bear and runs away. They then meet Promethus, the Genetor who guards the knowledge of atomic power, who's immortality has become a prison from the radiation. But Kortan has come for the quickening also. Finally Quentin relents and receives the quickening of atomic power.