You only live twice

In the comics, the characters cannot stay dead. Which is fine, and I don’t have a problem with it. However, on the big screen, things don’t work so well when a hero (or, very rarely, a villain) is brought back to life. It simply steals from the tension of a movie.
Coulson is, by far, the biggest of all offenders, with his death’s significance being annulled once he returned to life. We can also mentioned Professor X (disintegrated and then, in the same movie, revealed to be alive), Nick Fury, Bucky Barnes, and, of course, Superman (in this case, this is a double offense, since it was actually revealed in the same film that he lives – as if we didn’t see it coming).
And then, of course, there is Loki and there is also Zod, both villains being brought back to life, just because the script needed a good villain (maybe this isn’t so for the latter).
If a hero dies, it has an impact on the entire shared universe – reviving him as soon as possible makes me wonder if there is an actual threat in the shared universe for him. If a villain dies (as it happens so often), maybe he should stay dead.
If not, maybe the villain shouldn’t die, at all. After all, he is facing heroes and not killers.
