Superman, Vol. 1

The Ex-Superman!
Superman, suffering from power-loss, is rocketed to Morgu, the executioner's planet, by the Anti-Superman Gang. While there, he evades the executioners, becomes the new hero of slaves, and, finally, meets Supergirl, who has come to rescue him. She reveals that his costume was dusted by a Red Kryptonite-like dust which removed his powers by an allergic reaction. With the dust removed from his uniform, he becomes super again. She also tells him that the executioners of Morgu committed suicide after they failed to kill him. Superman and Supergirl return to Earth.
Clark Kent, Assassin!
Exposure to a Red Kryptonite-like substance causes Clark Kent to repeatedly try to kill Perry White.