Who could take down The Incredible Hulk?
Back in the seventies, when I was a boy, there was an issue, now classic cover, of The Thing vs. The Hulk. They were the two strong guys eveyone wanted to know about, so it was only fair that they had to fight. I don't remember the scenes of the issue but i doubt The Thing stood a chance other than using the stupidity of Hulk against him. (You can lead a horse to water...)
Anyhow what others, except for Cosmic generators like The beyonder or Celestials or Death..., stand a chance of bringing down #1.
My pick would be Thor - With his power belt on his strength is doubled. Plus he can summon a Storm of huge porportions and then strike with lightning, throw his hammer, and land some punches. If he finished him quick enough, before Hulk had time to get even madder, he may be able to knock him out solo.