Bowser had been a long-term enemy of Nintendo for his role in Team Xecuter, a group which designed and sold console modchips to allow the play of pirated games.
51-year-old Canadian hacker Gary Bowser has pleaded guilty to multiple hacking charges, must now pay $4.5m, and could also face up to 10 years in jail.
Torrentfreak reports Bowser recently changed his plea to guilty, admitting charges of circumventing technological measures and trafficking in circumvention devices.
Bowser was arrested and deported to the US after being found in the Dominican Republic.