Avengers: Endgame is a unique movie in that it had to service the story set up by 20 something preceding films as well as be its own standalone thing. Planning out a film that complex means a lot of things ultimately ended up being cut or changed during the production process.
It’s actually a miracle that Endgame turned out as good as it did because some of the original story ideas screenwriters Christopher Markus and Stephen McFeely had in mind for the film would’ve either traumatised you or bored you to sleep.
During their 2019 Comic-Con panel, Markus and McFeely revealed that there were originally plans to kill off Steve Rogers in grotesque fashion. An earlier draft had 2014-Thanos travelling to the Earth of his timeline and killing all the Avengers because he got bored waiting for Nebula to rejig the time machine.
After wiping them out, Thanos travels forward in time to 2023 and proceeds to drop the severed head of 2014-Captain America at the feet of 2023-Captain America before giving him the taunting clanger, “I killed you again, what are you going to do?”
Frigging hell. That’s chilling stuff.
Unsurprisingly, Markus and McFeely decided to cut the scene because the time travel mechanics need for the scene made everything even more confusing than it already is, it wasn’t really necessary narrative-wise, and Marvel weren’t too keen on traumatising millions of kids with a scene from a snuff film.
On the other end of the spectrum, the writers also had a different storyline cooked up for Thor in Infinity War. Whereas the Steve Rogers arc was nightmare inducing, Thor’s arc was just… boring.
Rather than teaming up with Rocket Raccoon and Groot to go forge Stormbreaker at Nidavellir, Thor got his shiny new axe by fighting a giant Midgard serpent and… oh wait, that was it.
No character revealing moments and no Rocket and Groot, just a big snake battle. The writers said that Thor’s story was “dark for a long time” because they hadn’t “done well enough” with the character until Taika Waititi came along and unrooted everything we previously knew about the Lord God of Thunder.
Dabbling in a bit more Norse mythology would’ve been cool but Markus and McFeely had the right idea in cutting it since the aftermath would’ve likely trickled down to Thor’s arc Endgame and made it less interesting if not downright boring.
Plus it kinda sounds like a big budget version of that weird side plot Thor had in Age of Ultron where he went to a cave for some reason and we all know how pointless that scene was.
All in all, the writers had some interesting ideas for where Infinity War and Endgame could’ve went but the final products ultimately turned out just fine as they are.
And besides, shoehorning in Thanos decapitating Cap and showing the head to a different version of Cap would’ve probably would’ve ended up hurting Endgame‘s box office earnings anyway.