Thanos (Earth-1604)

"I thought by eliminating half of life, the other half would thrive. But you've shown me that's impossible. As long as there's those who remember what was, they'll always be those who are unable to accept what can be, and will resist. I'm thankful, because now I know what I must do. I will shred this universe down to its last atom...and then, with the Stones you have collected for me, create a new one. Teeming with life, that knows not what it has lost, but what it has been given. A grateful universe."

- Thanos Thanos was a genocidal warlord from Titan, whose own main objective was to bring stability to the universe, as he believed its massive population would inevitably use up the universe's entire supply of resources and condemn it. To complete this goal, Thanos set about tracking down the Infinity Stones, as the combined might could wipe out half the universe.

In his native timeline, he was alerted to the events of the Infinity War by a time traveling Nebula, resulting in him traveling to her native timeline and laying siege on the Avengers, as he had just decided to instead wipe out the entire universe and replace it out of revenge for their efforts to stop him.