It's the Juggernaut, bitches! And it's his very first appearance from Uncanny X-Men #12!:
Dang it all! You weren't supposed to know about this device that is supposed to be a big secret even though we made it capable of emitting a loud, uninterrupted alarm sound (which it's doing right now)! Forget you saw Cerebro! And forget I called it Cerebro! Dammit, see what you made me do?
Since we know he's coming, can we turn off the loud shrieking thing?
There's no time to tell me what his power is, but there's time to tell an origin story?
Seriously, Professor, shouldn't we get out there?
Are you interrupting my story, Cyclops?
Uh... no, sir. Go ahead.
Wow.... there's no stopping older folks once they start telling a story is there?
Well, this was certainly more important than analyzing the Juggernaut's strengths and weaknesses! We're about to be slaughtered, Professor, but feel free to tell us how great you were at high school track!
I do, however, appreciate the use of the term "last desperate spurt."
By now, this story had better end with "And that's why you get to smoke weed with hookers for the rest of the day!" if I'm sitting through all this.
Yeah, by all means, Professor. We'll all die today, but at least you got to whine about your childhood. Glad you had a chance to get it off your chest.
Let me get this straight: The Professor spent the whole issue in flashback, and they basically forgot to lock the friggin' gate? Am I the only one rooting for the Juggernaut at this point?
Well, we've gone too far now! See the exciting conclusion Monday!