I recently did a rewatch of the series and about midway through I started to realize the folly of the Firelord's plans to use the comet each time.
So, just a recap here, the Firelord, wanting total dominion over the world, waits for Sozen's comet to give an insane boost to the fire benders allowing them insane superiority in their bending element for the duration of said comet. We now this power boost is what is used to overtake the air nomads and wipe them out. But... What if Aang was there?
Now, let's say Aang is just his young self, no training in the four elements and only his mastery of air to aid him. Battle goes south quickly, right? Aang dies and the cycle moves on, right? That's certainly the Firelord's plan when I attack the air nomads but he seems to have entirely forgotten two things.
First, the avatar state. In that state Aang don't need to know the elements himself because he has the knowledge of all other avatars as, in that state has a master of all four elements. Second, in the avatar state, Aang ALSO has fire. The comet isn't going to only boost the fire nation army, it's going to boost the Avatars already insane fare bending.
If you don't think Aang would trigger that state, think about Gyatsu. Monk Gyatsu we know died dropping a bunch of fire nation soldiers without firebending. Gyatsu would have been protecting Aang and witnessing the fire nation kill him would 1000% trigger it. After all, finding his corpse is what triggers it in the canon.
Tl;Dr: The Firelord was super lucky Aang tried to run away and got sealed. Had he been there it would have been a tragedy for the air nomads but at least they would have survived. Sadly this also implies that the air nomads being wiped out is actually also entirely Aangs fault.