...but its not realistic. Having the villain go to jail or always survive cuts half of reality away from storytelling potential, because there's no getting away from it: sometimes villains leave no other choice than to be killed. In Return of the Jedi, Vader did not just attempt to stop Palpatine (from electrocuting Luke) by using whatever power he had left to just hurt him enough to subdue him. He could have called Luke's lightsaber to him and cut off Palpatine's arms. He did not exercise any other option save for the one that was necessary--a finishing (killing) move to end the problem forever.
In Infinity War, despite Thor not getting it right (sequels, folks!), he did attempt to kill Thanos, not reason with him, or assume there would a way to subdue him. No matter how Endgame tries to work out the defeat of Thanos, in the film in question, Thor saw only one way to deal with him, which was the right approach. Life does not always give characters pleasant options. Its not pretty, or welcome, but it is necessary form time to time.