After the Kree experimented on Robert Hunter, he developed the ability to explode at will and thus took on the name Nitro. With a thought, the combustible criminal can detonate with the same force as 250 lbs of dynamite.
Regarded as a C-list baddie at best, Nitro became infamous after his actions indirectly led to Captain Marvel dying from cancer. As devastated as the superhero community was by this loss, it was, by no means, the worst thing Nitro did.
While facing off against The New Warriors in Stamford, Nitro blew up beside a school, killing 600 people, including 60 children. Although some suspected the scale of Nitro's attack was accidental, Wolverine discovered Hunter was paid by Damage Control to blow up Stamford so the company could make billions on the reconstruction. Wolverine also learned that Nitro took a power-enhancing drug so his explosion caused as much death and destruction as possible.
Even though Nitro was already known for being a killer, the attack on Stamford earned him a reputation as among the most reviled supervillains on Earth, as well as one of the most murderous.