Sadly there is disincentive to report bad workers on MTurk. You can block them through the MTurk system which rightfully puts their account at risk for terminat

Sadly there is disincentive to report bad workers on MTurk. You can block them through the MTurk system which rightfully puts their account at risk for termination. BUT Amazon sends them an email identifying you as the blocker, which causes them to go write terrible reviews of you on worker sites, which reduces the supply of workers for your HITs. So the ideal way to handle it is block them from your HIT server so at least they can't do YOUR HITs again and never report them.