History
Hailing from the Battleworld domain of Limbo, Hulk along with the Spider-Man, Ghost Rider and Wolverine was a member of Infernal Four, a group of bounty hunters who were allowed to cross between domains.
They were hired by God-Emperor Doom to apprehend the Punisher of Earth-27169 for breaking a law by crossing into another domain. Punisher wasn't operating under his own free will, though: he was possessed by the spirit of his domain's Doctor Strange. When the Infernal Four confronted Punisher in the domain of 2099, he killed three of them, including the Hulk.[1]