Wait, with the speed and scope of heat manipulation, wouldn't he be able to incapacitate or kill people on a whim? Human body needs only around a bit over five degrees of heating, before it starts to coagulate (imagine boiled egg). From what we've seen so far, even now he'd easily be able to do that with a large enough of an area, that the body can't even begin to self-regulate. If he focused on the brain, the wet mass would just bork itself and stop. Even better, human brain doesn't have any heat or pain receptors, so the target would literally have no idea that anything was wrong, before losing the ability to have that idea.
And that is just a single, simple use for his power. Only the 50 or so degrees of quick manipulation he already has been shown to do would make him more dangerous than any edgy blade-y boi.