Within the Abyss lie some of the most powerful beings in all of Dungeons & Dragons. If a DM or players are looking for beings of unmitigated evil and chaos, they need look no further than its denizens. When these creatures are not infighting or scheming amongst themselves, they are wreaking havoc across any plane they have been summoned to.
Source:https://www.cbr.com/most-powerful-dnd-demons-5e/