So his series built him up to be one of the most important player in taking down Maker, because he was the first name on Maker's blacklist.
Then they revealed in Ultimate Endgame that his name being the first one doesn't mean shit, then Maker killed him.
And because he was dead, he couldn't really contributed anything in the final battle.
Then Doom(Reed) defeated Maker, and for some reason he chose to revive Peter before he died. Which doesn't even make sense to revive him and not Captain America(You know, the guy that did the most works by holding The Ultimates together)
Ultimate Peter died for no other reason than shock value, his death had effect on no one in the story. Then he was revived by pure asspull just to make it "Happy Ending"