The only thing he’s glad about is where his abilities manifested.
The villain of the day (look, he is not going to remember all of their names) is giving a frankly abysmal monologue as he corners Hiro with his chimeras. The rest of the team are handling their own, Baymax is grappling with some pterodactyl hybrid in the air, and there’s nothing to stop the chimeras from lunging at him when the villain gives his dramatic command.
He throws his hands up, expecting fangs and claws to tear through his armor and arm -
But heat suddenly explodes in front of him and there’s the smell of something burning, the sound of something crying out in pain. He opens his eyes to see the chimeras cowering away from him, the villain screaming at them to attack, you useless mutts, attack and he says, “thanks, Fred.”
But there’s no answering quip from Fred (who he finds out later was having some leaping contest with the kangaroo hybrid). There’s only him and the flames that are licking at his heat-resistant armour and he’s not burning, he’s not hurt.
It takes several more incidents before realisation sets in. In another life, he would have been so very excited.
In this life, all he can do is stare at the flames flickering bright and wild in the palms of his hands, stare and think. One year ago, and he could have helped. One year ago he could have went in and out of that building unscathed, he could have prevented - prevented -
The flames flare up and he extinguishes them with a clench of his hands, his nails biting crescent-shaped indentations into his skin.
He wishes that his skin would blister red and angry, would peel off and be charred into ashes, like anyone else would when they touch fire. It’s not fair, he thinks, petulant and furious, that he has this power when the person who should have had it didn’t. That he should have this power when it mattered the least - when it doesn't matter at all.
But like a moth attracted to a fire, Hiro snaps his fingers and conjures another flame up again, imagining worlds where he takes all the flames away before they could hurt anybody, before they could hurt Tadashi -
And hates himself for not being able to live in any one of them.