Reprints X-Men (1963) #42 and a 5-page story from Amazing Adult Fantasy #7
"If I Should Die...!"
The Professor has set a trap for the Sub-Human as he lures him to earthquake machine but Charles underestimates the creature as it is able to turn the machine on. The X-Men fight to get to the turn off switch but cannot get around Grotesk. Charles struggles to shut down the machine but Grotesk hits the Professor then destroys the machine and in the process, kills himself in the explosion, an explosion that takes the life of Xavier as well.
"Why Won't They Believe Me?"