10 Dead Characters Returning For Future Movie Sequels
8. (Most Of) The Guardians Of The Galaxy
How They Died
Aside for Rocket Raccoon (and Nebula, though she wasn't actually a fully paid-up member of the Guardians team), the entire Guardians line-up was killed in Infinity War. Gamora was killed when Thanos sacrifices her for the Soul Stone and the rest are turned to dust when the Mad Titan delivers on his threat to wipe out half of existence.
Strictly speaking, more than half of them are killed, but this isn't a maths lesson.
But Wait...
It might currently be on ice thanks to James Gunn's departure and the concerns over the cast following him out in a show of solidarity. That would be made difficult by their contracts, of course, but Marvel have to mend some things before they can make the sequel.
The point here is that the sequel has been officially announced and is still in development. That fact alone confirms that the Guardians are back from the dead. Otherwise it would be called Rocket Racoon On His Own Guards The Galaxy and that's not as catchy.
Will It Be Explained?
It will indeed, in Avengers: Endgame when the end of Infinity War is somehow undone and lots of dead characters are made alive again.