Star Trek: The Original Series
Where No Man Has Gone Before
S1 E3:
While exploring the energy barrier at galaxy's edge that crippled an earlier ship, Kirk's long-time friend and crewmate Gary Mitchell begins mutating into a god-like entity disdainful of the "mortals" around him. Can the captain overcome his own feelings for his friend before the new entity grows too powerful to stop?
Starring
Gary Lockwood, Sally Kellerman, Eddie Paskey