The son of the late Spencer Smythe, Alistair grew up around a father who frequently ignored him in favor of his obsession with Spider-Man. As a result Alistair grew up a bizarre young man, over-weight, poorly groomed and with perverse tastes in women. Alistair inherited, however, his father's knowledge of mechanics, and parlayed that into a job for the Kingpin, where he secretly continued on with his work on Spider-Slayers to finish his father's goal, the death of Spider-Man.
The Spider Slayers
The Spider-Slayers were a series of robots that sought to destroy Spider-Man. The initial generation of Spider-Slayers were created by Alistair's father, Spencer Smythe and commissioned by J. Jonah Jameson. After Spencer failed to kill Spider-Man - and ended up getting destroyed as a result - Alistair inherited the legacy from his father and gained a new-found hatred toward Spider-Man. He initially worked for the Kingpin but left in disagreement over how to deal with Spider-Man and went solo.
After being confined in an asylum, Alistair released himself and took several other inmates with him in order to construct a new series of Spider-Slayers that tracked Spider-Man across the city. His plan of revenge forced the inmates to assist in the machines' construction. After sending a series of slayers after Spider-Man (and all of their inevitable destruction with assistance from others including the Scorpion and the Black Cat), Alistair lured Spider-Man to his residence for one final battle.
In order to defeat Spider-Man on his own, Alistair enhanced himself by encasing his entire body in a biorganic carapace that not only served as a full body armor, but increased his strength and gave him the ability to walk again by interconnecting with his spine. The physical structure of the carapace gave Alistair bird-like talons for feet; a long, curved blade-like weapon jutting from each shoulder; a pair of smaller, jagged blade weapons on each forearm; and a specially made web-shooter that fired from the forearm area. Eventually, Spider-Man defeated Alistair and made sure he and the surviving asylum inmates were taken to custody.
During Scarlet Spider's brief stint as sole web-slinger in town, Smythe (still carapaced as the Ultimate Spider-Slayer) started a war with a new set of slayers he intended to sell on the black market. These Cyber-Slayers—which could be controlled remotely by turning one's thoughts into the slayers' actions—were probably named as such because the initial target was not Spider-Man nor Scarlet Spider, but Lady Octopus and her crew. However, as fate would have it, the Scarlet Spider ended up in the middle of things and temporarily allied with the Cyber-Slayers, a fact that did not go over well with Smythe.
Smythe found his way outside prison and sought revenge on both Spider-Man and J. Jonah Jameson for the death of his father. He coerced Jameson to alter the stories in the Daily Bugle or else he'd kill JJJ's wife and son. Once Spider-Man caught on to Smythe's trail, he followed it back to the Bugle where Smythe assaulted him with recreated versions of every Spider-Slayer ever sent after Spider-Man in the past plus a pair of new creations—a miniature model designed to latch onto Spider-Man's face and penetrate his mind through use of radiation and a larger six-armed model arguably stronger than any other created. While attached to Spider-Man's head, the miniature spider-slayer psionically connected to Spidey's mind, copied thoughts of his loved ones, and broadcast that information to all the other Mini-Slayers. Smythe gave Spider-Man the choice of either stopping them or preventing the Six-armed Slayer from destroying Jameson. Spidey eventually shut down all the Spider-Slayers at the same time, but it was Jameson who knocked out Smythe with a baseball bat for threatening his family. Smythe recently made another return in which he used a poisonous spider he made and attacked John Jameson, aka Man-Wolf and caused him to end up in the hospital.
He later invades The Raft with Boomerang, Scorpion, and Vulture, The Superior Spider-Man is seen fighting Alistair Smythe and is mocking him for being weak in comparison to his father Spencer Smythe. When the Superior Spider-Man says that he has called the Avengers for backup, Alistair Smythe states that he has his own backup as Boomerang, Scorpion, and Vulture show up. The Superior Spider-Man admits that the Mini-Slayers were clever but inadvertently reveals that his countermeasures are being powered by the Raft's Power Generators distracting him at the revelation. Alistair Smythe takes the upper hand until he's narrowly shot down by Mayor J. Jonah Jameson disguised as a Raft guard. The Superior Spider-Man accuses Mayor J. Jonah Jameson of leaving the force field, but Mayor J. Jonah Jameson confronts Spider-Man to tell him he brought him to ensure that Smythe gets executed by any means necessary (implying that he's giving permission to Spider-Man to directly kill him). The Superior Spider-Man accepts and tells Mayor J. Jonah Jameson to go back to the force field with the others. The Superior Spider-Man hunts Alistair Smythe through his comm system only to discover that he did the same trick and informed his allies (all heading for a full front assault against the Superior Spider-Man) who tries to convince them that Alistair Smythe is using them and will take back their enhancements once he's out. All of them agree that even though that might happen, they'll make the best of the situation against him. Alistair Smythe manages to reach the Raft's generators, destroying them to shut down the power in the entire island, allowing Lizard to escape. Once Alistair Smythe tries to escape, the Superior Spider-Man reminds him about the emergency generators. Alistair Smythe warns the Superior Spider-Man that just like he does with his Spider-Bots, he can see through his Mini-Slayers catching up on Mayor J. Jonah Jameson and the trapped civilians sending their locations to the group. Scorpion rejects it at first, but is easily convinced once Alistair Smythe tells him that one of his targets is Mayor J. Jonah Jameson himself. Scorpion heads for Jonah, Vulture aims at the civilians, and Boomerang stays to fight against Spider-Man who stops him by blocking his Bomb-A-Rangs with his webbing escaping the resulting blast in the process (and possibly killing Boomerang). Alistair Smythe warns him that he's still caught in a predicament since Scorpion is heading to his personal vengeance against Jameson and Vulture is ready to kill the group of civilians so he must make a choice only to be surprised when Otto replies that he won't follow any of them. Instead, the Superior Spider-Man is determined to complete his mission of slaying the Spider-Slayer
The Superior Spider-Man battles Alistair Smythe and after a long battle disarming him, As Alistair Smythe admits defeat and ask Superior Spider-Man for the terms of surrender, The Superior Spider-Man replies by stabbing Alistair Smythe with his own blade, killing him. This also disables Boomerang, Scorpion, and Vulture's upgrades preventing them from killing Jameson and the leaving them injured once again. As the three are subdued, Superior Spider-Man and the others exit the Raft only to be attacked by Alistair Smythe (whose body is being moved via his miniature Slayer robots). Alistair Smythe effortlessly disposes of the guards explaining that his mind is still alive for a few precious moments. Superior Spider-Man tackles Alistair Smythe, leading to them falling off the Raft and only to shore below. As they struggle, Smythe reveals his final plan to transfer his consciousness into Spider-Man and takeover his life. However, Doctor Octopus had already done this as he had encased his head with armored plating (as seen in Amazing Spider-Man #700) making Alistiar Smythe unable to initiate the transfer. As Alistair Smythe expresses confusion on why it did not work, Superior Spider-Man (out of the ear shot of anyone else) tells Smythe he did it before him and revealing his true identity as Otto Octavius. Superior Spider-Man taunts Alistair Smythe as he dies stating Smythe has no legacy as in his final battle he wasn't even fighting the real Spider-Man. Alistair Smythe dies as Superior Spider-Man moves away from the body with his secrets still intact.