"Mountain of Terror" is the story featured in issue #5 of Action Man.
Flying in a glider, Action Man finds Dr X's hideout on the top of a mountain, but cannot glide up there, so he discards his glider. He must climb, facing an eagle and rocks crumbling.
Action Man reaches Dr X and takes the cure. Dr X activates a trap that sends Acton Man down the mountain, but Action Man reaches his glider and flies away with the cure.