"The Universe will now be set right. Made over to fit my unique view of what ... My name is Thanos, and my name means Death."

There are villains and there are supervillains and then there are guys on the scale of Thanos... a force of nature made flesh. The 'mad god of Titan,' Thanos is a deranged and power-mad being of immense power. Deemed the avatar of Death, he literally courts the physical embodiment of the concept as one would a mate. Threatening all of existence on a galactic scale, there are few that measure up to the sheer destructive power that Thanos is capable of.

Introduced way back in the pages of Marvel Two-in-One (a Thing team-up book), Thanos was at first simply an intergalactic tyrant recruiting mercenaries from various worlds to build an empire. Rejected by his home world, Thanos sought to improve upon his already considerable might by the use of technological advancements as well as mental concentration. Turning his back on his own people of Titan, he built up an army only to return and destroy the surface of the planet and declared himself sole ruler of a dead world.

Possessing staggering strength and endurance, Thanos is also about to warp space and time, direct energies and move objects with the power of his mind. He needs neither nourishment nor air to live and seems to thrive on conquest alone.

As corpses fell in his wake one of the cosmic abstracts named Death sought him out. Hovering at his side, the spectral female image watched with interest as Thanos' mission of supremacy increased and the universe trembled. Discovering that he could remake reality through the cosmic cube, Thanos fought the combined superhuman forces of the Earth to obtain it and warped everything to fit his view.

Defeated by his own egotism, Thanos was shut down by Captain Marvel and shunned by Death for his failure. From that point on, he became obsessed with re-earning Death's attention. Fueled by a love for Death, he embarked on a quest to find the most powerful way to attract Death, leading him to the fabled Infinity Gauntlet.

Thanos assembled the mystical gems of Time, Space, Mind, Reality, Soul and Power and used the Infinity Gauntlet to challenge all of creation. All of Earth's superheroes united to fight Thanos, along with Adam Warlock who wore the soul gem on his forehead. The battle was cataclysmic, but in the end Thanos was again defeated. However, his devotion to Death and his staggering endurance meant that he would neither die nor would he stop in his mad schemes of carnage.

Drax the Destroyer

There have been many dedicated to the death of Thanos, such as Drax the Destroyer, a being created with that single imperative.  Thanos is not without his enemies, but even after finally killing Thanos and achieving his life-long goal, Drax was horrified to see that the mad Titan was needed to battle a threat far greater than anything he dreamed possible. Through a rip in space, dark gods from another universe both similar and opposite to our own (dubbed the 'Cancer-verse') found its way to ours and attempted to spill over into a fresh reality from their own where all of the resources had been used up.

As his legend had grown over the years, Thanos became synonymous with Death and was revived to be its avatar and champion. When our universe was invaded by distorted versions of the Avengers from a reality without death, just an unending form of life gone rampant, the Guardians of the Galaxy reluctantly recruited Thanos as their ultimate weapon. This of course had complications, but it also affirmed that he is as much of an abstract embodiment as Galactus, a cosmic abstract who is so powerful that he is nearly beyond good and evil.

... or maybe he's just a thug who needs to be taken down a peg.

Thanos is taken away by New York's finest

Recommended:

The Life and Death of Captain Marvel

Silver Surfer: Rebirth Of Thanos

Infinity Gauntlet

The Thanos Imperative