Almost every character who returned from 4 died..... ULPC, Packie(Optional), Johnny, Terry, Clay, Ashley, and others.
I'd rather not add Niko to that list.
ULPC being killed by the stupid part of the story (FIB),
Packie being killed by Trevor (Altruists Cult), optional
Johnny being killed by Trevor in the WORST way possible
Terry-Clay-Ashley being killed by TREVOR AGAIN in the worst way they could've think off.
But... Niko would kick Trevor's ass.
Hell, even Rocco Pelosi deserved a better death. Michael just killing him because he roughhoused Solomon is just stupid. The guy was made in the Ancelotti family, but it is never once brought up.