The first few chapters were good but they shot themselves in the foot. If they kept his power altering things by several degrees and made all his fights into "battles of the wits" where he would strategically raise temperatures in very specific places to gain the adventure instead of the sudden 180 into being OP as fuck, then it would have gone a lot better
Talk about a rushed ending that made no sense in context.
I'm gonna say that he doesn't even become unrivaled.
thats how it ends? if i had to describe it with one word it would be disappointing, the dude is a nuclear weapon and it has had a lot of build up and it all ends with him lowering and heating the room a bit, he never got to use or acknowledge his real power at all in the series.
it had potential it just never lived up to it.