It may be sort of traditional for deaths in superhero stories to be reversible, but Syndrome's sticky end in The Incredibles should probably, well, stick. One of the reasons he's an effective villain is that he's a dark mirror for Bob during Bob's days as an insurance claims adjuster. Like Bob, Syndrome wants nothing more than to put on a costume again and prove what he can do. He's a millionaire as it is, but he could become a mega-billionaire just by going straight to his backup plan of selling his inventions. He wouldn't have to hide on an island to develop his toys: he could just buy Google. But he wants to play "hero" so much, that desire clouds his decisions, just as it clouds Bob's. By the end of the movie, though, Bob is once again a committed family man, and Syndrome dies incapable of loving anyone but himself-- the reflection is broken. The Incredibles 2 needs a new villain who can similarly reflect the family's new reality, whatever that is.
T Campbell has written quite a few online comics series and selected work for Marvel, Archie and Tokyopop. His longest-running works are Fans, Penny and Aggie-- and his current project with co-writer Phil Kahn, Guilded Age.