Universe/Timeline:
Marvel Universe
The Frightful Four are the opposite number of the Fantastic Four, typically gathered and maintained by the Wingless Wizard.
Other members include Trapster, Beetle, Thundra, Brute, Llyra, Electro, Man-Bull, Dreadknight, Titania, Hydro-Man, Klaw, Red Ghost, She-Thing, the Punisher robot, Blastaar, Karl Malus, Wrecker, Thunderball, Bulldozer II, Gazelle, Reptilla, and Vertigo I.