Raxachk, from Martian Dreams
Raxachk is a martian and megalomanic that caused all of Mars to fall into ruin.
He was once an agrarian of the Grove of Argyre, but thirsted for power over all of Mars. He tried to gain power by seizing control over the oxygen and water distribution, while at the same time making political moves. Failing this, he resorted to terror, which resulted in him creating a deadly plague that in the end killed all martians -- even himself. However, everyone fled into the Dream-World, where Raxachk found his true powers.He became so powerful, that he essentially became the master of that dream world. He constructed new plans to lure Humans to Mars in order to take their bodies and then conquer Earth. He partially succeeded, and took the body of Rasputin.
It was then the Avatar arrived on Mars in Martian Dreams. The Avatar systematically undid Raxachk's evil until the martian was finally cornered in the Dream World. However, Raxchak was behind a seemingly indestructible crystal barrier. Although Raxachk's psychometric powers could reveal the truth through an individual's possessions, he didn't realize that the Avatar came from the future (the Avatar didn't carry things from the future). That was his doom, as the Avatar used a supply of Dreamstuff to imagine into existence a weapon from the future: an M60 Machine Gun. Raxack's barrier was useless against this weapon's might, and the martian was shot to bits, destroying his essence for all time.