Challenge of the Super Friends (1978)

The episode opens with...Batman's funeral! We soon find out that the Legion of Doom have a substance, Noxiam, that allows them to kill any Superfriend. In flashback we see Lex trick Superman into opening the krypton-steel box. Then the Riddler lures Batman into an ambush in Gotham City and kills him, leading to the funeral at the beginning. The Legion then takes the Daily Planet, Perry White, and Lois Lane hostage and kill Superman, and Paradise Island hostage to force Wonder Woman to confront them and be killed as well. The other Superfriends flee Earth but come back and are killed. Luthor then tosses the Noxiam into the sewer, its use at an end. A protectively garbed figure recovers it and shoots the crystal into space--it's Apache Chief. It's all a ploy to lure the Legion out. The dead Superfriends were actually robots.