If the JLA could do this so easily, what happened with the Burning? The Martin Manhunter is nowhere as powerful as Onslaught, and Batman had to buy time to find a solution. The combined powers of the Avengers, The Fantastic Four, The Xmen, Doctor Doom, Iron man, The Hulk, Cable, Apocalyps, and Magneto. Yeah the JLA could beat all of them too.
Onslaught's power base: Nate Grey Upon examination by Moira Mactaggert, she suggested his psionic powers rivaled that of a Phoenix Force-imbued Jean Grey[4][5]. In another instance, he was measured as having a psionic energy output matching that of the Dark Phoenix [6]
Franklin Richards: Franklin is an Omega-level mutant possessing vast psionic powers. According to Roma, Franklin's power was equal to that of the Celestials. These powers have manifested as telepathy, telekinesis, energy blasts of concussive force (in adulthood), precognition, astral projection and reality manipulation -- the ability to make a thought or desire a reality. However, being a child, his abilities are restricted to an extent by his limited control -- at any given moment his powers could spawn the unthinkable with something less than a thought, or risk temporary depletion if overly exerted.
Erik Lensher: Magneto has the ability to generate and manipulate tremendously potent magnetic fields, which fields he uses most easily to move/control ferrous metals (iron, steel, etc.) and to achieve a wide range of other effects.
Because his personal magnetic field (i.e., the magnetic forces surrounding his own body) repels projectiles and absorbs energy attacks, Magneto is invulnerable to most harm when his personal field is active. His force field has withstood enormous forces including nuclear explosions. He is capable of personal levitation and sustained flight at high speeds, and can survive in the vacuum of deep space. He can also purposely channel his powers through his body for the purpose of temporarily increasing his strength, stamina, and agility to superhuman levels. Magneto has been depicted using his powers to lift submarines and oil tankers through levitation or sheer physical force. The absolute maximum amount of material he can levitate with his powers is unknown.
Magneto is able to perceive the world around him as patterns of electromagnetic energy, and can perceive the electrical auras given off by living beings. He has also demonstrated the ability to produce electricity as well as electromagnetic radiation. In a few instances Magneto has demonstrated the capacity to produce a wormhole, and to safely teleport himself and others by means of the wormhole.
Xavier: Professor X is a mutant who possesses vast telepathic powers, and is among the most powerful telepaths in the Marvel Universe.Xavier's vast psionic powers enable him to manipulate the minds of others, warp perceptions to make himself seem invisible, project mental illusions, cause loss of particular memories, and induce pain or temporary mental and/or physical paralysis in others. Within close range, he can manipulate almost any number of minds for such simple feats. However, he can only take full possession of one other mind at a time, and must strictly be within that person's physical presence. He has displayed telepathic prowess sufficient to confront Ego the Living Planet, as well as confront and narrowly defeat Exodus.[96]
Man I don't know...I think Onslaught wins this hands down.