1300 on nightmare. If you're trying to kill him without using the collar, wait until you have enough attack to almost oneshot regular Ogres when you have tactical advantage.
At this stage in the game, you're better off getting more attack than learning Heat Up since Aura doesn't have a lot of ATK to buff yet and Heat Up eats into your action economy. Weapon coatings are also expensive and largely unnecessary this early on(you're better off spending a couple of days dodging fights, harvesting materials, and getting salary/upgrades at the workshop).
General rule of thumb is that Thunderbolt is your go-to counter-spell for enemies with wind-up martials. If you land it during the wind-up, they don't get to do their fancy wind-up attack.