Juggernaut's lack of feats makes debating him difficult. The only time he ever gets KO'd in the proper cinematic release is when he is depowered. But, at the same time, we can't also say that the only way to KO him is by depowering him, simply because it hasn't happened any other way, as that is fallacious reasoning.
The deleted scenes showed him being pierced by adamantium (but healing literally instantly, without even a drop of blood), and in that version, a massive electrical current directly to the brain (Logan stuck his claws into the back of Cain's head, and then had Storm electrocute them both) could KO him. But those scenes aren't canon, as far as I am aware.