Mac McGee (a.k.a.) The Bonecrusher is a comic book supervillain and adversary of Frankenstein. He was experimented after a car crash incident and was given adamantium placed infused within his bones. As a result, he became extremely buff and strong.
This is the history of The Bonecrusher over the course of the series run.
The Bonecrusher made his debut in Season 1, Episode 3, "The World on my Shoulders." There, the incident with him and Percy was revealed and how they broke up as best friends. Afterwards, he went crazy and managed to defeat Frankenstein and kidnapped both Percy and Jen. They fought again but Mac was able to still beat him. During their last confrontation, Frankenstein makes him go off the deep end, pushing his rage and ultimately defeating him. Mac was then placed in jail for rehabilitation.
The Bonecrusher returns in Season 2, Episode 1, "Team Dynamo Part 1." He along with The Ravine, Menace, Clownface, The Black Kotana and Bulletshed were taken out of jail by Dr. Magnus Mysterious. They were hired to exterminate Frankenstein. They succeeded and The Bonecrusher took lead as leader of Team Dynamo, often consulting with The Ravine. They kept on bashing and thrashing Frankenstein every chance they got. Season 1, Episode 2, "Team Dynamo Part 2" features the villains grow more powerhungry over who defeats Frankenstein. They manage to defeat him once again and he is easily outmatched. In their last encounter, Frankenstein got them to fight each other and easily defeated them from then. He along with the Comissioner put the villains back in prison.
Season 3, Episode 6, "Grudge Match" has the Bonecrusher released from prison. He teams up with both Clownface and Bloodhound to get back at Frankenstein. When finding his house, they raid it and beat Frankenstein up. When Frankenstein wakes up, Frankenstein is being watched by all of the rogues in prison in a brawl against The Bonecrusher. After a lengthy battle, Frankenstein wins and places Mac in a special prison that he made.
The Bonecrusher appears in Season 5, Episode 10, "Divide & Conquer." There, he was recruited by the Bison and some others as a team of tanks to take Frankenstein down. The Bonecrusher was more than a match for Frankenstein teaming up with Box Top. However, Frankenstein was aided by Nuke and The Bonecrusher was stopped.