One of the most shocking revelations during Marvel's Civil War was the introduction of Ragnarok: a clone of Thor created with cybernetic parts by Tony Stark, Reed Richards, and Hank Pym to help them turn the tide of battle against rogue superheroes opposing the Superhero Registration Act. However, the faux God of Thunder would ultimately go against its programming during the 2006 crossover, which resulted in bloody consequences for the combatants as the conflict escalated.
Created by Mark Millar and Steve McNiven in Civil War #3, Ragnarok appeared as a battle between the two factions of superheroes erupted in a destroyed chemical factory, wielding his own advanced technological copy of Mjolnir. While the heroes initially mistook him for Thor himself, the clone attacked the anti-registration forces led by Captain America and personally killed Goliath, who became the first fatality during the war between the heroes.
Appalled, Reed personally reprogrammed Ragnarok through an invasive surgery while Peter Parker learned Tony had used hair follicles recovered from the real Thor to create the clone, under the codename "Project Lightning." The shocking revelation and murder of Bill Foster would play a role in getting Peter to leave the pro-registration faction to side with Captain America. In the final battle, Hercules went on to destroy Ragnarok with his own hammer, crushing his skull.
Years later, Secret Invasion revealed that the Hank Pym that helped the development of the Thor clone was actually a Skrull imposter. Unbeknownst to Tony or Reed, the Skrull agent implanted a fail-safe code that had to be regularly put into Thor. With the Skrull Hank killed during the 2008 crossover, Ragnarok reactivated from his storage unit within the Avengers Initiative's training facility at Camp Hammond. Believing himself to be the true Thor, Ragnarok defeated the Avengers-in-training at the camp and the New Warriors before setting out to destroy the real Thor whom he believed to be an imposter.
After defeating Volstagg during crossover event Siege, Ragnarok confronted Thor only to be easily destroyed by him, proving no match for the real deal. Norman Osborn had his remains secretly recovered and rebuilt by A.I.M. to attack the New Avengers, with Wolverine and Iron Fist defeating Ragnarok once again. Ragnarok would be recovered and restored to join the latest iteration of the Dark Avengers, joining the team on a mission to an alternate Earth where he recovered that world's Mjolnir sometime after its own Thor had been killed by that world's Hulk.
Transformed into his own distinct physical appearance after claiming Mjolnir in Jeff Parker and Neil Edwards Dark Avengers #189, Ragnarok was pivotal in helping his teammates take on both the superheroes of this alternate Earth as well as A.I.M. when they attempted to close the portal between worlds to trap the Thunderbolts within it while preserving the space-time continuum. Ragnarok was last seen helping the team escape back to their own world in time in 2009.
It's been several years since Ragnarok has surfaced in the Marvel Universe, even after he acquired his own version of Mjolnir and had his latest inhibitor device removed. While the cosmically upgraded Thor would likely be able to best him again in a potential rematch, Ragnarok has certainly undergone his own upgrade -- and surprise heroic redemption. Although he stands as a living reminder of the extreme lengths undertaken by the pro-registration side during Civil War, Ragnarok is no longer a science experiment gone horribly wrong. Instead, he's his own antihero. And while he may always be regarded as a murderous copy of the God of Thunder, Ragnarok has come a long way from being one of Tony Stark, Reed Richards, and Hank Pym's biggest mistakes.