Functionally, there is no such thing as a living or dead anime character. They are fabrications of the mind, ink on paper, and pixels on a screen. However, their stories' sense of character and causality does a great job of suspending that disbelief and getting the viewer invested in the fictional lives of made up people.
And while on one end, a viewer may worry for the stakes and well-being of their favorite main character, it is the villains whose lives carry more immediate weight towards a story. They are the conflict whose relationship with a series' core themes is dictated by their own victories and failures.
There are assuredly plenty of villains who have been surmounted and killed within their respective series, but there are an infamous bunch who manage to sustain through seasons. This list will be celebrating the conflicts that won't stay down, as it runs through a few villains who should've died a long time ago (but did not).
10 All for One (My Hero Academia)
Perhaps the freshest entry on this list, All for One is a central antagonist whose very existence in the series to this point is near, purely defined by vague expectations. All for One's ability to survive not just one but two fatal interactions with All Might is possibly attested to some Quirk but that aspect certainly isn't obvious when looking at him.
The man is a ground up, veiny bruise of his former self who literally needs air tubes to consistently keep himself breathing and alive. With those signs of mortality, what exactly kept United States of Smash from ending him or even some government force from trying to get him executed? Given his vast crimes against humanity, one would think that would've been brought up.
9 Envy (Fullmetal Alchemist)
The regenerative abilities of the Sins in Fullmetal Alchemist is a mixed bag of expectations. While one knows that the Philosopher's Stones are consistently keeping them in tact, they have shown varying abilities to handle stress, whether that means the slash of a blade or being burned alive over and over again.
Perhaps the most dragging example of this in the series is Envy who, after being brought near death, simply devolves into a tiny, worm-like husk. While at one end this was used to humble Envy, it was just more of a way of keeping them alive yet sidelined despite clearly being beaten. Envy, however, would later die but at their own hands.
8 Johan Liebert (Monster)
Johan may be one of the few on this list whose persistence from the going to grave is not the result of anime powers but just cruel fate. Johan was supposed to have died by his sister's hands at a young age yet was miraculously saved by Dr. Tenma.
Seeing new life, Johan would use it to start a path of destruction to see how fragile and persistent life may be. After going through this path, Johan would once again be shot yet, somehow, would survive once again, saved by the Dr. Tenma once more. Life just doesn't want to keep this monster down.
7 Zeref Dragneel (Fairy Tail)
There is very little explanation for this one. Zeref is the main villain of Fairy Tail who was cursed with both immortality and a tendency to kill those around him if he cares for them. While he hatches this entire plot to create demons (Natsu in particular) capable of killing him, what eventually gets him is the same curse that he has from Mavis.
The two being deeply in love with one another use that love to fuel the curse that kills them both...possibly. The series from there suggests that they get reincarnated in, like, less than a year. How did he survive? Why did he survive? This isn't how reincarnation works!
6 Dio (Jojo's Bizarre Adventures)
It's a wonder if Dio will ever be fully kept down or if he'll just be sidelined until the next major event within the Jojo franchise. Dio should've seen an ultimate death at Johnathan's hands during the original series during a ship explosion. Yet, he survived in the most last minute, convoluted way, hiding in a tightly sealed coffin and taking control of Johnathan's body.
He would see a much worse fate at the end of Stardust Crusaders in which Jotaro literally punches him to death; but given how persistent a vampire can be, Dio may very well pop up again due to some form of plot armour and fans literally wanting more of him.
5 Hisoka (Hunter x Hunter)
Demented in every sense of the word, Hisoka is a despicable character in the world of Hunter x Hunter who is always being actively hunted by someone looking for revenge for whatever thing he may have done to them before. This has meant some of the best mercenaries and martial artists in the world going toe-to-toe with him, some even managing to hit or even maim him.
Despite various people around the world trying to kill him, only one person, Chrollo Lucifer, has managed to deal a lethal blow, doing so by letting dozens of people explode on top of him. Hisoka, in an amazing display of resilience/anime nonsense, managed to use Nen to get his hand to pump his own heart several hours later.
4 Sir Crocodile (One Piece)
Sir Crocodile was arguably the first major villain in the series to actually feel like a legit threat against the Straw Hat crew. He was a member of the world's most elite pirate alliance and an honored figure throughout Alabasta whose own conspiracy was tearing the country from the inside out.
He even managed to brutally beat Monkey D. Luffy twice, before Luffy eventually got his comeuppance, literally punching him several hundred times through the ceiling of an underground ruin, pushing Crocodile through several feet of stone before landing him in the city streets above. Crocodile would somehow survive all of this just to be arrested after awards.
3 Madara Uchiha (Naruto)
After the series essentially forgot about Orochimaru, Madara and his legacy essentially became the big bad of the series, bringing a villain legacy that was near unstoppable.
After being defeated and killed by Hashirama several generations prior, Madara would use the Izanagi technique to rewrite his own death, allowing him to live on. Madara would die much later though after entrusting his will to Obito, only to be revived as the series neared its climax.
2 Team Rocket (Pokemon)
Jesse, James, and Meowth, the romantic and passionate members of Pokemon's most consistent trio, should be dead by now. They've been hit by lightning, blasted by laser beams, been through explosions, and launched several miles into the air.
They really shouldn't be surviving any of there falls. "Team Rocket is blasting off again!" should be less of a comedic punctuation, as it is a death rattle of a group of people seeing a grizzly demise, something met by the group in a variety of hilarious yet utterly gruesome ways.
1 Frieza (Dragon Ball)
Frieza is proof that popularity and nostalgia really does trump all, even life and death. 14 years after being killed by Goku at the end of the Frieza Saga, two of Frieza's minions would collect enough Dragon Balls to wish him back to life. After training and concocting new villainous plans, Frieza would actually get to destroy the entire Earth, before Whis turned back time to let Goku kill him once again.
This would not be the end for the iconic villain however, as the Tournament of Power called for the biggest ensemble cast in the series' history, where Goku literally requested for Frieza to be brought back from Hell. After having to be resurrected once more (this guy sure does die a lot) at the end of the arc, Frieza would reclaim his throne as Emperor of Universe 7.