Speaking of ridiculousness and an edge of darkness added to Charles Xavier, the Onslaught Saga was an attempt to really delve into the hidden side of Professor X whilst providing the X-Men with a crossover event that would actually have an effect on non-mutant characters. Which it did. But never a good effect. Onslaught was a new villain, a giant with crazy psychic powers and some Magneto-esque armour. It turns out the bad guy is actually Xavier, who absorbed some of Magneto's worst personality traits after trying to get him to go straight, which combined with his own repressed dark side and manifested in this monstrosity. The event pulled in the Avengers and every other Marvel hero too, with Captain America, Iron Man, Thor and the Fantastic Four all being seemingly killed off (only to be brought back in the terrible Heroes Reborn form). It's a pretty boring story, with a silly baddie, and only existed to bring about a reboot of other heroes. Whom Fox don't own.
Tom Baker is the Comics Editor at WhatCulture! He's heard all the Doctor Who jokes, but not many about Randall and Hopkirk. He also blogs at http://communibearsilostate.wordpress.com/