The MCU is usually considered to be very family-friendly. You can take the kids on a trip to the theatre and be safe in the knowledge that if a Marvel film is playing, it should be suitable. Until you start to think about the fate of the villains. Heroes for the most part survive their stories (though not always, RIP Iron Man and Black Widow), but the villains very rarely make it out alive.
Marvel films are almost always action films. There are fight scenes, and the heroes sometimes get a little bloody, but for the most part, it’s pretty tame stuff. We may see see them looking a little worse for wear and walking with a wince after a fight, but overall they make it out okay. The villains are less lucky, and though we don’t see the gory details of their deaths (got to keep that PG-13 rating) they are actually quite nasty.
One Marvel fan on Reddit has taken the time to list out the many villains and their current status, pointing out if they are still with us or if they have passed into the great beyond. In some cases, some of these villains died twice… sorry Thanos. Not only have they listed their current status, they also created a handy graphic to show just how many villains have kicked the bucket compared to the ones that are still with us.
The death of these villains has been pretty brutal in a lot of places. Ronan the Accuser was disintegrated by the Guardians who used the power stone against him, Kang the Conqueror was reduced to nothing as he was pulled into a quantum explosion (so we think, at least), Malekith was crushed, and Thanos was beheaded in one version and then dusted in another.
The few villains that have managed to make it out alive are mostly locked up in some way or another, be it in prison, (like Helmut Zemo who is aboard the Raft) or some form of purgatory, a bit like Agatha Harkness who was trapped in her own mind by Wanda Maximoff. There are a few villains still traipsing around out there, and we are keeping a wary eye open for them. Then there are those whose death is a little ambiguous, we’re looking at you Scarlet Witch!
Perhaps they will appear again, perhaps this is not the end for them. After all, we got to see Killmonger again in Black Panther: Wakanda Forever despite his death in the first film, so anything can happen.