In full metal panic kaname died in season 3?

That's not quite right! While Kaname Chidori is a central character in Full Metal Panic!, she does not die in season 3 (or any other season). In fact, she's one of the main protagonists and remains alive and well throughout the series.

You might be thinking of another character or another anime series. If you can remember any other details about the character you are thinking of, I might be able to help you figure out which character or series you're remembering!