Thermite was a sleeper agent member of the Squadron Supreme
recruited by Nighthawk
to betray the group after they had gone too far with their use of brainwashing technology for making the world a better place. Thermite's fellow recruits who were there for this purpose were Haywire
During his brief time with the Squadron, Thermite reveals a penchant for being a trickster as he plays multiple practical jokes on his teammates including interrupting a romantic moment in a hot tub between Haywire and Inertia by freezing the water solid.
In the Squadron Supreme's final, violent battle with these Redeemers
, Thermite is seemingly killed by mistake by Haywire as Haywire uses his powers to trip up the Whizzer
who, moving too fast to stop, kicks Thermite's equipment that's mounted on his back with such force that it explodes, freezing Thermite in a giant block of ice.
There has been another Thermite who has appeared since, but whether it is the same man or somebody new in the same outfit is unclear. This new Thermite is recruited into the New Enforcers
and comes into conflict with Spider Man
Thermite was able to shoot beams of ice and fire, though he is wearing equipment from his back that is generating this, so his powers are likely weapons based and he likely has no actual powers of his own. He once mentioned that he had to wear his suit often, so it is likely that it was invented for some sort of medical condition which he has, although that has remained unrevealed (and will likely never be revealed).