I think non-Ultimate fans underestimate Ultimate Reed. He is really not to be trifled with. The only time he's really been flat out beaten is by an infinity stone. (albeit lodged in Tony Stark's Brain) Heck, he pretty much wiped out Western Europe, THEN wiped DC off the map and the only way they could stop him is when he extended the olive branch and said "I don't really want any more, so you don't mess with me and I won't mess with you." He was arguably as smart as 616 Reed BEFORE he locked himself away for 1000 years and enhanced his mental capability and built a basically unstoppable city. Ultimate Reed is at least cunning enough to take out the rest of the Cabal. I really think 616 Doom is the only person who will be able to stand up to him.