X-Man

The "X-Man" was a one-shot Marvel villain created as part of an educational comic about child safety - as such he was a "themed" villain and arguably one of the more evil-minded antagonists in the series despite his small role due to his crimes being more rooted in real-world events (albeit with superhero elements added in).

The "X-Man" was a serial child-molester who took to dressing up as a superhero so that he could play on children's trust/wonder - claiming to be a mutant with "special powers" he would appear at playground and try to spirit children away.

However he was stopped by the real X-Men, who exposed him as a criminal and Wolverine threatened to show the pedophile some "tricks" of his own as he took the "X-Man" away to an unknown (but likely unpleasant) fate..