Looking for a manhwa

Hi. I am looking for the title of a manhwa that I used to read before. It starts in a school where kids get bullied. Then the protagonist with a mysterious history comes and teaches some bullies a lesson. However he also trains some kids mma who were getting bullied. He then takes them to an underground fight club where the his students had to fight in a group mma fight of 4v4 or 5v5 in an elevated ring where the only way to lose is if you fall from the ring. Does this premise ring any bell? I would appreciate the help.