It was Onslaught who punched Juggernaut clear across North America. And Juggernaut survived, although he was badly injured.
Funny enough, that was one of the suggestions I was going to make for a third movie: at the end of the second film, with the Blob and most of the other Super Villains dead or overthrown, the Juggernaut suddenly re-appears. He has been tortured and beaten to the point of death. He uses the last of how once great strength to grab Logan's arm and tell him that Onslaught is coming...
Third film opens with a flashback: Charles Xavier was not at the X Mansion when Wolverine was manipulated into killing the X Men. He was attacked by Magneto. As Xavier was dying, Magneto taunted him with the knowledge that all his students were being murdered, that Charles' dream of peaceful co-existence with humans would never come to fruition. Instead, Magneto plans to gather all Mutants under his power and, eventually, overthrow Doom himself.
Enraged, dying, Charles' self-control finally snaps. He unleashes all his Telepathic power in one single burst of psychic energy, intending to trap Magneto's mind in a never ending illusion based on his memories of the death camps. Magneto would spend the rest of his life reliving the murder of his parents and the other Jews in Auswitzch, over and over again.
However, this backfires spectacularly. It unleashes all of the repressed anger and frustration of Charles Xavier's long life, all the times he was tempted to simply bend other people to his will rather than trying to convince them he was right. All the Mutants and human friends he had lost. Every dark impulse and desire he ever felt - all of it combining with Magneto's limitless rage, his hatred for humans and his unshakeable conviction that Mutants can never live peacefully alongside Humanity. They must kill or be killed.
The result is Onslaught: a being combing the worst aspects of Professor X's and Magneto's personalities, and the full range of their immense Powers. He kidnaps and tortures the Juggernaut simply as a test. He wanted to practice using his powers on one of the strongest beings on earth. Now he is ready to carry out the next phase of his plan...