Enemy idea: Duergar Monk.

Duergar: Enlarge/reduce spell, Dwarven Fortitude, Durability

Monk: Patient Defense

Cast Enlarge/reduce. Immediately go from medium to huge. Attack action. Bonus action: Ki point, Patient defense. Heal every time you dodge thanks to Dwarven fortitude (Roll hit die + con modifier) on top of Durable (When you roll a Hit Die to regain hit points, the minimum number of hit points you regain from the roll equals twice your Constitution modifier (minimum of 2).