Marvel seems to have a problem with villains, particularly keeping them alive. Of the twelve movies that have come out, most people only remember one or two villains and that is Tom Hiddleston's Loki and Josh Brolin's Thanos. The other villains are either killed or are very forgettable including James Spader's Ultron. Even potentially awesome and very important villains within the comics themselves have been killed or disappear. My example for these are Baron von Strucker played by Thomas Kretschmann and Ronan the Accuser played by Lee Pace.
Strucker and Ronan are very important within the comics and have time and again caused many problems for the Avengers, but in the movies they are killed as either the main villain (Ronan) or killed like a wimp (Strucker). I found their deaths very insulting and I believe that Marvel had made a mistake killing both Ronan and Strucker. I would have liked to see at least Strucker longer, if not in a movie at least within Agents of Shield prompting a better story line than what has proceeded within the show.
Keeping Ronan alive would have been a good choice too for we could have seen him with the Kree Supreme Intelligence which would have made the cosmic realm of the MCU far more interesting to see.
Another villain that seems to have a problem is Mandarin. When the trailers for Iron Man 3 came out, everyone thought that Ben Kingsley's character was indeed the Mandarin. He looked the part and even sounded menacingly like the Mandarin. Not only that but it seemed like he had a connection back to the Ten Rings we saw in the First Iron Man. But as we know, the shocker was Kingsley's character wasn't the Mandarin, but simply an actor portraying the Mandarin, while it was Guy Pearce's Aldrich Killian who was actually The Mandarin which was very disappointing to many including myself.
Nearly every other MCU villain has been boring and forgettable and it really stinks because Marvel has so much potential if they could just keep some of these villains alive. All these big villains keep dying and only the smaller lesser henchman seem to survive and escape. I am referring to of course Sam Rockwell's Justin Hammer, William Hurt's General Thunderbolt Ross, and Karen Gillan's Nebula. These three are alive and some of them have escaped and I hope to see them again in later films but the fact remains Marvel keeps killing their villains and while that is necessary for some of them, not all them deserve death and instead to be placed in some sort of maximum security penitentiary.
Now comparing the MCU to the Netflix MCU, Netflix does a better job at keeping its villains around. Daredevil had Wilson Fisk/Kingpin played by Vincent D'Onofrio who does an excellent job but we also see in Daredevil, Madam Wu, who most likely has some connection to Iron Fist, and from what we know of Season 2 of Daredevil we know The Punisher is coming who will be both villain and Anti-Hero. Jessica Jones had Kilgrave played by David Tennant, now if you haven't seen it spoilers but he is killed at the end which he deserved based around what he had done to many different people. But Jessica Jones also set up another villain known as Nuke. So for now the Netflix MCU already has a better track record for its villains than the normal MCU.
If Marvel wants to keep going with their success and still pleasing fans they need to start improving their villains like their Netflix counterparts or like DC in the comics where they keep their villains alive and in jail.