Arguably the most feared (unless you're Thanos, of course) of all the cosmic entities in the Marvel universe - and understandably so - is the embodiment of death. Often manifesting in the form of a lady - Lady Death - but also appearing in the classic "Grim Reaper" form, Death is the all powerful cosmic force of nature that decides who and what lives and dies in the Marvel universe. Although Death rarely speaks - usually getting her agents to speak on her behalf - we get the gist of what she's about. She has complete control over souls and, if she wanted, could switch souls between bodies, send souls to hell, leave souls trapped in an intangible state or do whatever else she wished to do with them. As well as the ability to kill anyone she chooses, she can also gift (or curse, depending on how you look at it) any living being with eternal life - such as what has happened with Deadpool. She is worshipped by the Mad Titan Thanos, who is actually in love with her and most of what he does is simply to impress her (such as the events of the Infinity Gauntlet story arc). She is completely immortal and invulnerable, possesses vast cosmic awareness powers and vast energy manipulation powers.
3. The Living Tribunal
A lot of you probably thought this guy would be in the number two position right? Well, maybe he should be, but the reason that he isn't will be revealed after you click "next". The Living Tribunal is a singular entity who exists across the entire Marvel multiverse. His true purpose - i.e. the task for which he was created - is to protect every single world indefinitely. He safeguards existence itself from mystical and cosmic imbalance and transcends the realms of death and eternity, order and chaos and all opposing realities. His appearance ("the Trinity") is very relevant to his function. His half cloaked face represents vengeance, his cloaked face represents necessity and his full face represents equity. He uses all three faces to look upon the universe and make judgements (hence his name). Concepts such such as good and evil, right and wrong or happy and sad have no meaning the Living Tribunal and he is concerned only with what is ultimately right for the good of the universe in the long term (whatever those consequences are in the here and now). He possesses absolutely unlimited power and is able to erase whole realities from existence. However, he has no free will and is bound to the wishes of the One-Above-All.
