<Snipped quote by RBYDark>
Okay. I should have explained better. I was thinking that it could be introduced as a threat to everyone, but... it's like saying "You have to fight Superman" but what you mean is "You have to fight Superman, but he won't use his heat vision or ice breath."
Except this is our own Millenniummon and we can set whatever parameters and limitations on him that we want/need. He literally just formed and is a feral asshole; that's far from the worst excuse for him not to be able to pull together the power to blow a dimension apart.
And like RBY said; if you're insistent on him being able to do these things, feel free to volunteer Jordan and Shrewmon for a demonstration.