Jack O'Lantern is the name of the five supervillains who appeared in Marvel Comics. He is a member of Thunderbolts. Some incarnations were known as Mad Jack.
The original Jack O'Lantern was disgraced ex-CIA Agent Jason Macendale, who assumed the identity after several years working as a freelance mercenary. Macendale was primarily a foe of Spider-Man and during his time under the alias, formed a working relationship with Hobgoblin.
A second Jack O'Lantern, named Steven Mark Levins, was introduced in Captain America v2 #396, who fought Captain America and Spider-Man while in the employ of the Red Skull.
Following the death of the second Jack O'Lantern at the hands of the Punisher, Daniel Berkhart, who previously operated as Mysterio, became the third Jack O'Lantern and worked primarily for Norman Osborn, once again as an enemy of Spider-Man, as well as Daredevil. Jack O'Lantern was later revived by Lucifer and had new abilities such as Reanimating the Dead to do his biding and became an enemy of Ghost Rider.
An unnamed man who claimed to be Steve Levins's brother has since been caught by the police. This man was shown to be able to transform into a Jack O'Lantern-headed villain using the powers of a mystical demon. The police interrogated the man, but he was later released by Norman Osborn who wanted this Jack O'Lantern in his army.
After Osborn's fall, a new Jack O'Lantern appears working for the third Crime Master. As a child, the kid that would become Jack O'Lantern has disobeyed his parents and maltreated animals. When going as Jack O'Lantern for Halloween, he came across a house that Crime Master was in and gassed. Crime Master took the boy under his wing and trained him to be an assassin. It was with this training that Jack O'Lantern had killed his parents. Jack O'Lantern claimed that he had killed anyone that has used the Jack O'Lantern mantle. One of his jobs brings him into conflict with the government operative Venom. During this conflict Flash threw a live grenade into his mouthpiece and it dislocated his jaw. Even after the explosion he was still able to run and retreat. Later, Crime Master is able to use contacts to discover Venom's true identity, and has Jack O'Lantern kidnap Flash's girlfriend, Betty Brant, in exchange for Venom letting Crime Master get his shipment of Antarctic Vibranium. When Venom leaves to rescue Betty, he is distracted by Spider-Man's appearance, which drives the symbiote into an uncontrollable rage. Eventually Betty is rescued at the last second by Spider-Man, with Venom then trying to recapture Crime Master. However, Venom is attacked by Jack O'Lantern, who proclaims Flash as his first real arch-nemesis, and desiring revenge for the disfiguring grenade explosion, also mockingly calling Flash by his first name, "Eugene". While it has not been confirmed, this new Jack O'Lantern claims to have killed every other person to go by the name in an effort to "clean up the brand". Jack O'Lantern is a member of the Crime Master's Savage Six.