Creeped Out features a different antagonist for each episode, but some of them aren't exactly human.

Here are all the antagonists who appear in Creeped Out:

Slapstick: Mr. Blackteeth

Cat Food: Mrs. McMurtle

Trolled: BillyGoat356

Marti: Marti, the titular smartphone

A Boy Called Red: No antagonist

The Call: Pui

Bravery Badge: Unnamed alien creatures

Spaceman: The titular spaceman, or Stan(named by Thomas)

Kindlesticks: The titular character.

Shed No Fear: The Shade

The Traveller: The Traveller