Peter knows he aborbs powers right?
So wouldn't he use his blood and give it to Nathan?
Or Claire now knows her blood saved Noah. Nathan's assassination is public knowledge. Wouldn't she just call?
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Also why does a shot to the head kill Peter/Adam, yet a shot to the head to Noah doesn't mean the end of him because he got blood from somebody who can regenerate?
Only three people know that Claire's blood can return someone from the dead.
Noah and Bob, and neither of them are bringing back Nathan. And Claire, who may try it since he was her biological father...but also may see what happens when you try to go public.
Again, Peter has no idea what his abilities really are. It's easy for us to say "Well Peter can do everything everyone else can" but in reality he can't. He is an uncut diamond.