Britney

Disgusting. Unarmed Strikes have disadvantage against Britney.

Creepy. If the party is in an area with Britney, no one can leave that 400 x 400 ft area until Britney is defeated.

Idol. All monsters with a wisdom or intelligence score lower than 10 are simps for Britney.

Social (non) Distancing. Any creature who breathes air within 5 ft of Britney gets the poisoned and stunned conditions.

Angel's Looks, Devil's Personality. All creatures fighting Britney have disadvantage in saving throws against being charmed by her.

Sleeptalker. Britney can use spells with verbal components while unconscious.

Getting to Their Heads. Britney can stack the effects of spells cast with her charisma modifier.

Resting B***h Face. Britney never loses concentration on debuff spells unless she concentrates on another spell. She can stack the same spell, however.

Harvest. Britney recovers a first level spell slot every time she does damage to a creature.

Spellcasting. Britney is a 2nd level spellcaster. Her spellcasting ability is [Charisma] (spell save DC 19, +22 to hit with spell attacks). Britney has following Bard spells prepared:
Cantrips (at will): [Vicious Mockery], [Friends]

1st level (20 slots): [Charm Person], [Bane]

2nd level (10 slots): [Suggestion]

Legendary Resistance. Twice a round when Britney fails a saving throw, she may succeed instead.

Britney has 2 attacks, which can be spread in any way.

Bully's Untouchability. Area of Effect Attack: DC 16, 60 ft radius from Britney, On Saving Throw Failure: 1 force damage, disadvantage on all attack rolls and saving throws, and incoming attacks against the affected creature have advantage.

Fake Fingernail Scratch. Melee Weapon Attack: +10 to hit, reach 5 ft., 2 target. Hit: (1) [slashing] damage. Blinds creatures on hit.

Epic Queen Beam. Ranged Magic Attack: +16 to hit, range 7/200 ft., 2 target. Hit: 1 [radiant] damage. Hit creatures are incapacitated for their next turn.

”Beautiful Smile”. Area of Effect Magic Attack: DC 18 (CON saving throw), affects all creatures currently watching. Upon Save Fail: creatures who fail the save are so disgusted that they gain disadvantage on all attack rolls and ability checks.

Lob. If Britney is near a monster or player character that is large or smaller, she may move them up to 40 ft in any direction, just not through obstacles.

Randomize. Britney is so stupid that the attacker questions their entire existence. They now have to roll their attack with no bonuses. It can sometimes hit random places too. This is done in exchange for 50 of Britney's hit points. This ability also lowers a saving throw DC down to 10.

Britney can use 3 legendary actions (resets after Britney takes damage).

Substitute (Costs 1 Action). Britney secretly teleports to a place in the area she is trapped with the party members in of her choosing, leaving a doppelgänger that has all the same abilities as Britney and 100 health behind in exchange for 10 hit points. Upon dying, the doppelgänger explodes and blinds everything within 10 ft of it. Doppelgängers cannot use legendary or mythic actions.

Tantrum. (Costs 2 actions). Britney summons a total of 5 CR 3 monsters that do her bidding.

Britney has 1 mythic action, which comes into effect only after her health reaches 0.

I'm Back. Britney is back. But wait, there is more. Her action economy and legendary actions have both doubled. Now Britney has 4 attacks and 4 legendary actions. She has become even worse. Also, her health comes back to full, and all spell slots are refilled.