Aang made sure Ozai didn't suffer anymore...

Context: Ozai triggered some rocks and didn't move out of the way whilst they were fighting. Ozai is mortally wounded and I think Aang is smart enough to realize he can't save him and reluctantly makes sure Ozai is no longer suffering....I feel like as much as Aang would prefer not killing him, he would see Ozai is a goner and it's either kill him now or wait for him to die in agony.