Bowser is a member of Team Xecutor, one of the world's most "notorious videogame piracy groups" which has become infamous for creating tools that exploit vulnerabilities in Nintendo, Sony and Microsoft video game hardware. The tools in question allow end-users to overcome protective measures put in place by hardware makers in order to run unofficial software, with game piracy being one of the most notable uses.
You might recall Bowser was hit with a $4.5 million fine last month after being charged in a federal lawsuit with 'Conspiracy to Circumvent Technological Measures and to Traffic in Circumention Devices' and 'Trafficking in Circumvention Devices'. The Team Xecuter member agreed to waive his right to be tried before a jury and has pleaded guilty to the two charges.
Things have gotten worse for Bowser, who has now been hit with a separate $10 million fine in order to settle Nintendo of America's civil case against him. Bowser has agreed to pay this fine, too.
In September of this year, 51-year-old Canadian national Bowser was arrested alongside 48-year-old French national Max Louarn. It's worth noting that the fines discussed here are to be paid solely by Bowser; other defendants will be charged separately.
Speaking in 2020, Team Xecutor insisted that it was not "a copyright-infringing ring of software pirates" and that it was unhappy with Nintendo's "censorship" and "legal scare tactics".
Back in April, Nintendo successfully obtained an injunction against another company selling Switch hacks, Winmart.