Well, what is your definition of powerful ? The evil janitor from Ang Lee's "Hulk" movie said that his irradiated poodles were powerful, but they were just plain embarrassing. Much like the rocket launching Penguins in the 2nd Batman film, starring Paul Reubens. They have much to answer for...
If we're talking scale and sheer "Oomph", then it's Galactus' stop-watch by a landslide. If it's versatility and usefulness and near infinite applications then the Mother Box is supreme.