Nargak

Nargak was a villain from the World of Fantasy comic book of 1958, published by Marvel comics - long before the company would become a powerhouse in the superhero fantasy department : as such the stories of this era were mostly self-contained and akin to works such as Tales From The Crypt, Creep Show or the Twilight Zone.

History
Nargak was a rogue among an unnamed race of humanoid aliens who sought to make peaceful contact with Earth, due to his violent and hateful nature he was forbidden from taking part in his people's attempts to reveal themselves to humanity but took it upon himself to steal a powerful weapon and some small-scale resources so as to wage a one-alien war against peace.

Nargak planned to completely eradicate the entire Earth, using a "Martian" missile - he was ultimately stopped from doing so when a law-enforcer from his own people was assigned to stop and apprehend the criminal : in the resulting confronting he was forced to shoot him dead to prevent the deaths of billions, reasoning the lives of the entire human race outweighed the life of one insane alien.

Traits
Nargak was a humanoid alien who possessed roughly the same strengths and weaknesses of any human male, however he was much more dangerous than most humans in the fact he was driven by deep and unreasoning xenophobia : to the point he was willing to utilize advanced alien technology to kill the entire population of Earth (which in 1950s would of been around 2 billion at minimum).

His signature weapon was a large mortar fitted with a "Martian" missile, which was said to have enough power to completely destroy the world - he also carried a smaller fire-arm and had access to teleportation pads : he was a criminal among his kind and thus was likely denied their more advanced technology or resources and was a lone wolf, with no aid from any others.

Trivia

 * while many aliens in the 1950s, 60s and 70s were referred to as "Martians" this does NOT mean Nargak or his people were actual natives to Mars - the more likely theory is that they simply used Mars as a stopping-point or colony (of course in real world terms the use of the word "Martian" in these eras was simply another term for any alien - regardless of origin).