To harass.
To make into a monster; to categorise as a monster; to demonise.
To behave as a monster to; to terrorise.
To play (a series of) non-player characters as directed, without having the responsibility of organising the game itself; generally not limited to playing literal monsters or hostile combatants.
Great; very good; excellent.
Very large; worthy of a monster.
A terrifying and dangerous creature.
A bizarre or whimsical creature.
A cruel, heartless, or antisocial person, especially a criminal.
Something unusually large.
A prodigy; someone very talented in a specific domain.
A badly behaved child, a brat.
A non-player character that player(s) fight against in role-playing games.