Being a PG-13 franchise owned by Disney, the Marvel Cinematic Universe doesn't really have a lot of scope for extreme acts of violence like that of Deadpool and Logan.
I mean yeah, it's a superhero movie and there is a lot of violence going around. But it has never been as extreme as the two movies mentioned above.
Well, if the initial plans for Avengers: Endgame had been finalised, things could have been a lot trickier.
According to Cinema Blend, at some point during developing the film, the writers had toyed with the idea of Thanos taking Captain America's head off.
Endgame writers Christopher Markus and Stephen McFeely revealed this bit of information during the San Diego Comic-Con.
McFeely said that Thanos had been a bit busy in 2014 after finding about the Avengers' plans.
He (2014 Thanos) had even gone to the Earth of his own time, destroyed it, killed the Avengers, and waited until Nebula opened the rift in 2023... It was The Hellscape. Giant Man's body would be behind him, the Avengers have all just been totally destroyed, and he throws something out in front of the Avengers and they go, 'Oh my God, it's Steve's head.
- Stephen McFeely
Of course, this wouldn't have affected 2023 Captain America. But you can see how confusing that might have been for a lot of people, given that Nebula had already killed her former self by then.
But that still would have been pretty interesting and massively fucked up. But then again, the Mad Titan of the comics has already done it.