"Unus, the Untouchable!" (X-803) by Lee and Kirby/Stone.
Scott Summers leads the X-Men, with Professor X off on an adventure. Cyclops has trouble holding the team together on his own, and the Beast leaves the team, trying to make some money as a pro wrestler. He encounters Unus the Untouchable, a mutant whose power is to repel anything that comes at him. Beast sees that Unus is being recruited by the Brotherhood of Evil Mutants. Soon the X-Men confront Unus, but it takes the scientific mind of Hank McCoy to devise a victory over Unus.
First time that Iceman achieves "ice" form.
First appearance of Unus the Untouchable.
Reprinted in Marvel Super-Heroes (Vol 2) #27.
Pin-up of the Beast by Jack Kirby.