The Anti-Monitor fuses with his brothers to become the Ultra-Monitor and fight their mother. They are able to hold back Perpetua but due to Doom's influence empowering her and Hawkgirl straying from the plan, the Ultra-Monitor is defeated when Perpetua gives the Anti-Monitor the Anti-Life back, restoring him to his Pre-Crisis appearance and changing allegiance to Perpetua. Anti-Monitor is sent by Perpetua to kill Hawkgirl and Shayne, who Perpetua has stranded in space and prevented from returning to Earth. Before he can kill the two, the Anti-Monitor is struck by John Stewart/Green Lantern, who was driving the Flash's Speed Force car, forcing the Anti-Monitor back into his Rebirth appearance and releasing the Monitor and World Forger. The Anti-Monitor cries out for his mother's help, which he receives in the form of the fiery remains of Earth-44 which Perpetua flung towards his location. Anti-Monitor is one of the most formidable foes ever faced by the heroes of the DC Universe. He is directly responsible for more deaths than any other known DC supervillain, having destroyed thousands of universes. He was powerful enough to kill Supergirl when she became distracted. He consumed thousands of positive-matter universes to increase his power and was able to personally battle scores of the multiverse's strongest heroes simultaneously. During the "Blackest Night," the Anti-Monitor was reanimated as a Black Lantern. However, Nekron was unable to fully control him and thus was only able to subdue the Anti-Monitor to be used as a power source for the Black Lantern Corps' Central Battery, much in the same way the entity Parallax is the power source for the Yellow Lanterns' battery. The Anti-Monitor was also responsible for the death of Barry Allen, the hero better known as the Flash. After capturing Barry because his ability to traverse the multiverse unaided made him a dangerous variable, the Anti-Monitor created an anti-matter cannon that would destroy the then-five remaining Earths with a concentrated beam much faster than the wave of entropy he had originally unleashed. The cannon was destroyed by the Flash when he escaped and forced the energies of the weapon's power source into itself, causing it to explode and Barry to disintegrate. In addition to possessing vast size (varying from about nine feet to hundreds of meters tall), vastly superhuman strength, extraordinary durability (by the end of the "Crisis" series he was able to effortlessly withstand blows from Superman and even surviving a blue star going supernova), the ability to project destructive bolts of energy, and greatly augmenting another being's powers (as he did with Psycho-Pirate, whose powers were increased to levels too much for him to handle), the Anti-Monitor also possessed reality-warping abilities, which he displayed by removing Psycho-Pirate's face.