He is not morally grey he kills people he doesnt see as worthy of life he is morally RED
Morally grey describes characters who are neither purely good nor purely evil, but instead possess a complex mix of both qualities. They often make choices that seem questionable or even harmful, but are motivated by complex reasons, personal values, or circumstances.
They may help others, but they might also hurt them or commit actions that are clearly immoral.
He helped people but killed others in the process. ^^
I think Guwon is one of the most interesting morally grey characters I've seen in a while.