The Public Safety Commission are the main antagonists in the first season of Rosario+Vampire.
They're a group of enforcers on school grounds charged with protecting the academy. These members use their status to their advantage, similar to hall monitors, and anyone who opposes them is delivered swift punishment through methods of imprisonment and torture. They collect tribute and bribes from clubs, and if they do not pay, they will be shut down.
The Public Safety Committee have a long-standing rivalry with the Newspaper Club for exploiting their true nature, and had decimated the previous Newspaper Club in the past, leaving Gin the only member.
According to Deshi in the anime, she, Kuyo, a bespectacled male who becomes a cerberus, and a tall, sadistic male who becomes a golem are referred to as the "Four Kings".
In the end after Tsukune's identity is revealed (both manga and anime) it is likely the Headmaster removed the corrupt members from the School Police and replaced them with ones that actually did their jobs without becoming corrupt as they do not cause trouble for the Newspaper Club (or anyone else for that matter) afterwards
Their True Identity
The Public Safety commission are actually a group of thugs who harrass the students in Yokai Academy. They abuse their power by assaulting, false accusing, and mentally/emotionally abusing kids most of the time for no absolute real reason.
They mainly cause trouble and chaos for fun and they show absolutely no remorse.
In a fanfiction where Kuyou long already killed Tsukune, to the point where even vampire blood is pointless, Moka unleashes a level of power in which she could not ever dare to achieve, even with the seal broken. She goes into a ballistic killing spree, ending the lives of everyone in the PSC quickly except for Kuyou himself, whom she took her time with (slowly until he begged for death).