Avengers: Endgame featured two versions of Thanos: the original one who unleashed The Decimation in Avengers: Infinity War and his younger self from 2014. The older Thanos was surprisingly taken off the board early into Endgame when Thor beheaded the Mad Titan, and this twist came about when writers Christopher Markus and Stephen McFeely failed to figure out a compelling way to continue his story. McFeely recalled:
What is a two hour movie where you’re playing cat and mouse with that guy or trying to get him or punch him in the face or steal stones from him. The comics, which are lovely, he just sort of decides to tie one hand behind his back, that’s how it’s solved there, so at one point in the room we’re getting real frustrated. ‘What is the story here?’ I think Trin Trahn, our executive producer, just said ‘God, I really wish we could just kill him.’ And we all went ‘Wait a second, could you? What does that mean?’ And it sent us down this whole road where we solved the issue in the first, what 12 minutes.
Christopher Markus and Stephen McFeely sat down with directors Joe and Anthony Russo for the Avengers: Endgame home media commentary, and once original Thanos’ came around, they shed some light on this shocking moment. Having already delivered an entire movie showing Thanos collecting the Infinity Stones and wiping the floor with nearly every major Marvel hero, it was difficult to imagine what to do with the antagonist next.
Remember, even though the Infinity Gauntlet was damaged after Thanos snapped his fingers, the Infinity Stones were still intact at the end of Avengers: Infinity War. Had they been kept around, Thanos still would have been practically invincible, and even with Captain Marvel’s help, it’s unlikely the surviving heroes would have beaten him.
So instead, the writers decided to just heed executive producer Trin Trahn’s suggestions and kill Thanos. After he channeled the Infinity Stones’ powers to destroy them, Avengers: Endgame’s main heroes arrived to take him down. With his life’s mission complete, Thanos didn’t put up a fight, and Thor, still angered by how he failed to stop the Mad Titan from destroying half of all life in the universe, went for the head.
Joe Russo added in the Avengers: Endgame commentary that eliminating Thanos at the beginning of the movie allowed the narrative to become more introspective. As he put it:
What’s great about it is allows for a very different kind of movie. One that’s reflective and pensive and character oriented.
He’s certainly right about that. With the villain gone and no way to reverse the genocide, five years passed between Avengers: Endgame’s opening and the rest of the movie, and we saw how all the main characters dealt with life post-Decimation. Even when they all reunited to obtain past versions of the Infinity Stones in the Time Heist, there wasn’t an antagonist actively getting in their way… at first.
Then came younger Thanos, who didn’t have any of the Infinity Stones, but was just as determined as his older self to bring about his vision of balance. Once he learned about the heroes’ time travel mission, he had his version of Nebula pretend to be her 2023 self and open a portal to the present day to allow him and his forces to invade Earth and seize the Infinity Stones. This Thanos also decided that rather than eliminate half of all life like the original Thanos, he’s just destroy and rebuild the universe in his image.
Alas, things didn’t work out well for this Thanos either, as Tony Stark used the Infinity Stones to turn the warlord and his army to dust, an action that cost him his life. So Avengers: Endgame killed off two versions of Thanos, and while there’s the possibility he could be seen again, whether it’s further back in the past, through resurrection or even as an alternate universe doppelgänger, for now his story is finished.