King Maxx, formerly known as Anti-Maximillian, also known as Evil King Max, was the former king of Anti-Mobius.
King Max was a complete despot, who was dethroned and cast into the Moebian Zone of Silence by his daughter Anti-Sally and her boyfriend Evil Sonic. However, Anti-Max was able to not only survive, but thrive, bringing the entire Zone under his rule. This rule was not to last though, as the Zone Cops eventually came and arrested him, due to the threat he posed to other Zones.
Stuck in Zone Jail, Maxx once again thrived, bringing the Moebians and other prisoners under his rule inside the jail. When Scourge ended up in Zone Jail (having ironically been dethroned himself shortly before), Maxx made a deal with the Sonic doppelganger: if Scourge did not attempt to threaten his rule, Maxx would keep his cronies from killing Scourge. Scourge, his speed removed due to the Control Collar and his quills cut short, had no choice but to agree to the proposal.
At a later time however, Maxx believed Scourge to have violated their deal when he heard about the Destructix entering the jail and supporting Scourge. While initially complimentary of Scourge, bearing no apparent ill-will for his dethroning and even approving of Moebians taking new names to step out of Mobius' shadow, the former king's tone turned dark as he ordered his minions to kill Scourge, despite the green hedgehog's denial of involvement with the Destructix.
Fortunately for Scourge, the Destructix arrived just in time to save him, beating up King Maxx's goons in the process. When Fiona stated that Scourge belonged to them and wasn't to be touched, the angered former king responded by telling them they had just signed their death warrants, which only earned a mocking response from Fiona.