Death

"Humans. They are not the cowering wretches we were promised! They stand. They are unruly and therefore cannot be ruled. To challenge them is to court...Death."

- The Other to Thanos

Death is one of the Cosmic Entities in the universe.

Powers
Unlimited Ability To Manipulate Reality, Space, Time, Energy, Molecules, Life Force, Magic on a universal Level. Making him Nigh Omnipotent

Nigh Omniscient

Nigh Omnipresent

Biography
The walls of the Temple Vault on Morag displayed the four entities that created the Infinity Stones: Entropy, Infinity, Death, and Eternity.

After Loki's defeat in the Chitauri Invasion, The Other told Thanos that humanity was not as weak as they had predicted and battling them is "to court Death," to which Thanos smiled.

Trivia

 * "Death embodies decay and can possess the soul of a living being. Often taking the form of a woman, Death can manipulate reality, time, and space, and came into existence at the same time as Entropy, Eternity, and Infinity. Immortals are immune to death's ability. Thanos wanted to rule the universe with Death. Trying to impress her, he killed all life in half of the universe with the snap of his fingers."


 * In the comics, Thanos is in love with Death, to the point that he once obliterated half the universe to please her.
 * In an interview, Josh Brolin expanded on Thanos' relationship with Death, and confirmed that Death will be portrayed as a woman in the Marvel Cinematic Universe: "His relationship with Death, who is actually the woman, I love that. You can take  (in which Brolin plays obsessed with ) and pump it full of steroids, and then you have Thanos. I like that he’s motivated by that — not just motivated by destruction or death or this or that. He’s motivated by a very identifiable, human trait."