Doctor Elliot Franklin was a former government-contracted scientist who was tasked by S.H.I.E.L.D. with designing & creating various weapons for military application. Franklin fell out of favor with his government employers when it was discovered that he was also covertly designing & creating weapons for the criminal Maggia organization for a hefty sum. Fired & arrested for his connections to the criminal organization, which refused to offer aid to him in any way following his arrest, Franklin decided he would use his scientific expertise to become a criminal force of his own to pay back both the government & the criminal outfit who turned its back on him. To this end, Franklin, while in prison, gathered what materials he could to cobble together, such as his initial wrecking ball arm device, to escape from prison and go into hiding.
It was while in hiding after his escape from prison that Franklin perfected his initial wrecking ball gauntlet design and created the criminal identity of Thunderball in order to pursue his new criminal goals. Daredevil quickly ended this career shortly after it began, and Franklin was thus sent back to the Vault for his crimes, only to be immediately bailed out afterwards alongside several other prison inmates by Arnold Brown using the remains of former agent Werner Von Strucker's expensive funding and set to work as a HYDRA-employed heavy scientist.
Meanwhile, Loki, the usurper god ruling over Asgard, was looking for more methods to keep Thor occupied on Earth while he set about his goals to collect the Infinity Stones for Thanos, and he noticed that Arnold's HYDRA force dedicated towards rebuilding the organization from Hive's treachery was more than enough to fit the bill on his ideal "distraction". So, he manipulated events to have the completed Berserker Staff recovered from underneath the wreckage of HYDRA's barbershop headquarters, and sent it to Brown's HQ to have it examined for experimentation. Not only that, but Loki also used his magic to duplicate the amount of Centipede serum that could be used for Super-Soldier serum and delivered it in massive gallons to Arnold in disguise. Eventually, Loki's manipulations would break off to a point where Arnold would commission Dr. Franklin to have several of his finest brute warriors experimented on with one of the few intact Centipede Devices, giving them massive superhuman strength and durability. Franklin, in particular, was the last chosen to be experimented upon despite his objections that he preferred remaining on the sidelines as a scientist, but he soon learned to accept his newfound position upon realizing that his Wrecking Ball gauntlet had equally been empowered to new heights by a Berserker Staff piece...much to his growing blood-lusting pleasure. He has since gone on to serve as the Wrecking Crew's personal scientist and schemer, while also helping out in combat from time to time.