Help me find a kdrama I watched

I do not know if this is the right place but all I can remember is the end where the detective looking for the culprit whos killing people as revenge finds him in a house. His junior shoots and kills the culprit against the detectives wish and the culprit reveals that it's not the end of revenge but there's an organisation who helps each other out for revenge and the revenge will continue for others

Can you remember the episode no?

I checked but I don't think it's that. Thank you for helping i just can't remember which show it is.