Ingrid

With ridiculous base stats and some very high damage multipliers, Ingrid is one of the hardest hitters you will find in the game. She can also switch between single-target or AoE, has an extended range, and also applies burning or Radiant Erosion. On top of this she is a Watcher Lord, receives a damage increase in the arena, and has dual faction membership with the Arbiters, so can be paired with some of the other top units in game. Anywhere you can fit her in, she is top tier.