Thanos, the mad Titan bent on destroying half of the universe, finally got out of his space chair and is ready to fight. In battle, Thanos can become tired and will become slower and less powerful. He has two abilities:
Thrash- a simple melee attack that causes massive damage. You even begin to wither just like in the movie.
Laser- in the comics, Thanos can shoot lasers and so in the boss fight, he can too. He can only shoot lasers for a while before he gets tired.
If you kill him, you will receive his head and the Infinity Gauntlet, an item that gives you much power when worn on your off hand.