In the ending of Spider-Man: No Way Home, we witnessed Tom Holland’s Peter teaming up with Andrew Garfield’s and Tobey Mcguire’s Peter and developed a cure for the five villains.
Then the trio manages to turn every villain back to their human form, and with Dr Strange casting the last spell, they will now return to their respective Universe.
As the five villains now have been cured, they will no longer cause any harm to anybody in their Universe.
Lizard, Green Goblin and Electro are now freed from their evil super-human abilities, and they have now returned to their normal form. So Lizard, Green Goblin, and Electro will now return to their Universe and continue to live on and not cause any havoc.
For Doctor Octopus’s case, his death might be uncertain as of now, the reason being in the Spider-Man 2 film, he died while saving the New York city from the miniature sun he created.
But now, Thanks to Peter, his mechanical tentacles are in control in Spider-Man: Non-Way Home.

So when he goes back to the exact point, he might be able to drown the miniature sun in the river in a different way than one which he did on Spider-Man 2, and therefore, there is a chance that he will be able to save New York City without sacrificing himself.
Next, coming to Sandman, he never wanted to hurt anyone from the beginning. He just wanted to go to his daughter, and as per the ending of Spider-Man: No Way Home, he has now turned into his normal human form thanks to the combined effort of Tobey, Andrew and Tom’s Peter.
So now, when he returns to his Universe, he will not be causing any issues will not die for sure.
Lastly, coming to Tobey Maguire and Andrew Garfield’s Spider-Man, they will now return to their past lives where Andrew will continue to be a Spider-Man and live a happy married life with Mary Jane.
On the other hand, Andrew’s Spider-Man will also move back to his own Universe, where he will continue to be a Spider-Man will keep on helping people. And we hope he finds someone like Gwen soon in his Universe.