Several teams calling themselves the Lethal Legion have appeared over the years.
The first was organized by Eric Williams, the Grim Reaper, to seek revenge on the Avengers for the apparent death of his brother, aka Wonder Man. Members included Swordsman, Power Man, Living Laser, and Man-Ape. They resurfaced fighting the West Coast Avengers with the Reaper, Man-Ape, and Power Man (now Goliath III) joined by Nekra, Ultron-12, and Black Talon. During Dark Reign, the Reaper and Nekra teamed up with Absorbing Man, Grey Gargoyle, Tiger Shark, Mister Hyde, and Wonder Man for another Legion.
The second version of the Lethal Legion was organized by Count Nefaria. He also recruited Power Man and the Living Laser, plus Whirlwind. Nefaria later replaced Power Man with Grey Gargoyle, and his third Legion was an all-new roster with Unicorn, Volga Belle, Skullbuster II, and Moonstone.
Grim Reaper, Whirlwind, Living Laser, and Radioactive Man assembled briefly as a Lethal Legion during a prison break, mingling the above rosters.
The Hell-Lord Satannish made a different Lethal Legion out of condemned souls, including Zyklon (Heinrich Himmler), Coldsteel (Josef Stalin), Cyana (Lucretia Borgia) and Axe of Violence (Lizzie Borden).
The Grandmaster assembled an alien Lethal Legion to oppose the Challenger and his Black Order for a game. These included Captain Glory, Drall, Metal Master II, Ferene the Other, Mentacle, and the Blood Brothers.
Also, a comically random group of super-villains appeared once in Marvel Age Annual #1, calling themselves the Lethal Legion before a fight broke out in the Marvel Comics offices.