This Star Trek TNG episode called "The Survivors" touches on the theme of powerful beings in human form.
The Enterprise detects a single house on a devastated planet where this pleasant old boy (left) lives with his wife.
Picard offers to evacuate them in case the alien enemy might come back to finish them off but they refuse to leave, insisting they're "quite safe".
Later it transpires that the chap is a being of immense power in human form who has single-handedly wiped out the entire enemy alien race to ensure they never come back.
He reveals his true form at the end (right), he's quite peaceful and has no beef with Picard-