Worldbreaker Hulk? Unrestrained? You mean he wouldn't suppress his power and rage, and say, "Perform surgery on me, Dr. Doom. I won't use a small step to destroy the Eastern Seaboard. And I promise I won't unleash tons of power and without actually doing anything other than power up, destroy the entire Dark Dimension. Really, I'm doing pretty much everything except bending over."
But Ultron was able to take over Earth, not even Hulk, Sentry, etc. could stop him. Hulk destroyed the Dark Dimension just by powering up, and Sentry pwned Molecule Man. They had to go back in time to stop Ultron. Ultron is an underrated BEAST.