Falcon ( put 50 sigs on him) then Collosus. Then Tigra if you you learn how to play her. Then Hulkbuster if by then you dont have a better tech.Kingpin and Stealthy are also good rankups, mind you, but imho Falcon beats both in utility and ease of use, specially since he is duped. Kingpin kinda needs not only to be duped, but also to have high sig, that is why Falcon is better... with Falcon you get exactly 50% of his damage increase just with 50 sig levels. Stealthy doesn't t really need his sig ... I mean its nice to have but not as important as Falcon or Kingpin.