Years ago when the Avengers first started, Iron Man found a strand of hair that had fallen off of Thor's head. Tony kept the hair sample in case he might need it for later use in the future. When the New Warriors attempted to gain ratings for their reality show by capturing a group of escaped supervillains, Nitro used his explosive powers which killed most of the New Warriors and children at a near-by school at a wide range. The government then proposed the Superhuman Registration Act to have all people with super-human powers register with the government. When the Superhuman Registration Act became law, Tony knew that they would need some serious strength on their side and the time had come to use the strand of Thor's hair. Stark created a clone of Thor from the strand, working with Mister Fantastic and Henry Pym, who unbeknownst to Stark, was actually Skrull impostor Criti Noll.
The Pro-Registration side eventually set a trap for the Anti-Registration group, who were now known as the Secret Avengers. When the Secret Avengers attempt to escape, the Thor clone used his mechanical hammer to blast a hole through Goliath's chest, killing him instantly. The Thor clone continued his assault until the Invisible Woman uses her powers to protect the Secret Avengers and allow them to escape. The Thor clone was immediately shut down and taken back to base. Once they returned, Reed Richards began to examine what could have gone wrong with the clone.
Nick Fury and the Winter Soldier are watching the Civil War from an undisclosed location, and the horrors of war. The Thor Clone attack is one of the incidents they view.
Ben Urich a Daily Bugle reporter investigating the Civil War is shocked when Thor (actually a cloned cyborg version created by the pro-registration faction) kills Goliath.
Storm and Black Panther faced off against the clone. The fight ending with Storm creating an EMP in the Thor clone's brain.
Later, when Captain America surrendered to authorities, and the Superhuman Civil War had ended.Hercules destroyed the Thor clone, seeing to it that this clone could commit no further atrocities.
Iron Man and Captain America meet in secret at the abandoned Avengers mansion to work out the Civil War one last time. They debate their views on the registration act while talking about past conflicts. The Thor clone as one of the atrocities of the war. The Thor clone is one of the subject mentioned in Tony Stark's battle report when he views the international response to the SHRA.
Under repair at Camp Hammond, the clone was activated by a safety measure built into it by the Skrull that posed as Henry Pym, Criti Noll. Thinking he was Thor, the clone retook his hammer. But when Baron Von Blitzschlag told him that he was simply a clone, he was killed for it. The clone, codenamed Ragnarok, went on a rampage, easily dispatching the Initiative and the New Warriors, who rushed to stop his violent march of destruction. Baron Von Blitzschlag, who survived his previous encounter with Ragnarok, confronted him, goading him into attacking him with lightning, which only strengthened the old man.
Ragnarok was about to vanquish Von Blitzschlag with pure physical force, when the crafty Baron dismissed the notion as futile. He stated that while he could easily kill everyone here or even in the world, this would not change what he was in fact: an android-clone of the real Thor. Unconvinced, Ragnarok was shown proof that such methods were possible when one of the Scarlet Spiders revealed he and his "brothers" were all clones as well.
Blitzschlag told Ragnarok that the real Thor was living in Asgard, which was now physically in the realm of Earth (or Midgard), floating above Oklahoma. Ragnarok resolved that it mattered not whether he was or wasn't a clone, but rather that his warrior's resolve was true. He flew off to presumably confront Thor and his fellow Asgardians and battled Volstagg during the Siege of Asgard. Ultimately, Ragnarok was killed by the real Thor. 
Ragnarok's body was recovered by A.I.M., who lacked the resources to repair it. However, when A.I.M. joined a reborn H.A.M.M.E.R. they finally were able to, and Monica Rappaccini promised to rebuild it for Norman Osborn's new team of Avengers. They fought the Avengers on Osborns behalf but were eventually defeated and imprisoned together with Osborn.
After the Thunderbolts went missing in the timestream, the Dark Avengers were recruited as a replacement team. They were implanted with nanites in order to prevent them from going rogue, and placed under the leadership of Luke Cage. On their first mission Ragnarok and the Dark Avengers were sent to the new nation of Sharzhad.
Much like the original Thor, the Thor clone's strength, endurance and resistance to injury are greater than the vast majority of his superhuman race and most superhumans. He is immune to conventional disease, and highly resistant to injury. His flesh and bones are several times denser than a human's. However he wasn't anywhere near as powerful or as strong as the original Thor and only possessed a portion of his power and strength. While the real Thor was at the very least an equal to Hercules in hand-to-hand combat and clearly superior when using his hammer, Hercules defeated the Thor Clone and crushed his head with his own hammer although the clone was able to do surprisingly well against Hercules and held his own for a period of time.
Despite this, Ragnarok was still a force to be reckoned with, as he was able to effortlessly take on Storm, killed Goliath, and was taking on the entire Initiative and defeating them by himself.
Alternate Mjolnir: After realizing his status as a clone, Ragnarok was able to wield the hammer of an alternate universe's fallen Thor.
Formerly Mjolnir Replica: The Ragnarok possesses a man-made hammer similar to Mjolnir in design, which enables the Thor clone to project powerful electrical energy from the hammer and seemingly control the weather to an extent with it as well.