The Mysterious Melter

A former business competitor of Tony Stark's, turned deadly foe of Iron Man in Tales Of Suspense #47.
An unscrupulous industrialist, Bruno Horgan was a businessman who competed against Stark Industries for military contracts. He was driven out of business when Stark discovered that Horgan was using inferior materials to build tanks.
Later, Horgan accidentally discovered a way to melt iron when a testing beam malfunctioned. After studying the broken device, he unlocked its secrets, building a compact ray that could melt iron like a flame melts butter. Donning a cape and mask he sought revenge against Stark as The Melter.
It should be noted that his ray doesn't actually melt anything--It is not a heat beam. What the beam does do is disintegrate the atoms of any material at which it's aimed--Including IM's armor.
Thought drowned in a drain pipe after their first meeting, The Melter reappeared in T.O.S. #89. He escaped from prison intent on forcing Tony Stark to build him a highly miniaturized version of his melting gear. A new helmet allowed him to shoot even more melting rays at Shellhead. His gun now had settings for wood, flesh, stone, and metal.
The Melter came back in IM #92 with a redesigned costume and improved heat ray, making him "stronger than a handful of H-bombs." He reduced IM's armor to molten slag, but in a quirk of fate, he ended up drowning again--swallowed by the roar of breaking waves.
But it's hard to keep a good man drowned. Melter somehow ended up in jail again. While there, he was aided by a nuclear physicist who was in for a tax wrap. The scientist helped the Melter design a ray attuned to the metal in Iron Man's armor. Needless to say, this also failed.

Weapons: Various Melting Beams (chest-mounted and hand-held)

 (Excerpt used by permission from the Iron Man Armory database)