Leon Nunez is a Marvel character so lame he doesn't even have a superhero alter-ego, and his power is so awkward, its explanation on the Marvel wiki is almost as long as his entire character biography.
In a nutshell, Nunez is a mutant with the ability to give other people superpowers, via tattoos that roughly correspond to that power. So, if Nunez wanted to grant someone the ability to fly, he'd give them a tattoo of some wings, or if he wanted them to be able to shotgun Jägermeister, he'd give them a tramp stamp. You may notice that giving someone a tattoo is an incredibly convoluted and time-consuming process, meaning Nunez is next-to-useless in an actual fight, unless you give him 3 weeks notice and know exactly what you're up against.
On top of this, every time Nunez gives someone a magic tattoo it requires a portion of his "will" to work, meaning every tattoo slowly saps away at his own strength, as shown in the first nine issues of the Young X-Men series. When the limit of his power is reached, Nunez will fall into a coma and die. For some reason, Nunez never tries to tattoo himself, so his actual story arc in the comics is that he gives 100 random people new superpowers, falls into a coma, and is promptly never heard from ever again.