I say Peter Parker. I would have said Steve Rogers since it is because of him that mutants exist,but it was Peter's blood that everyone was after. If I remember right Peter's blood was very valuable. It was suppose to be some odd number multiplied to the original super soldier serum(or OZ they were basically the same thing) and that was one of the main reasons Nick Fury watched over him, besides there kinda father/son bond. There were so many stories around Peter's blood it was pretty much the staple for a lot of almost his whole run in UU. He also crossed over to so many different titles.