He hated himself. Minho couldn't forgive himself for what was done to you because of him. He couldn't protect you; the sight of your wounds tore him apart. No matter how much he tortured the perpetrators of your pain, he couldn't get rid of the unbearable emptiness in his chest.
Minho realized that he was the main danger to you.
His uncle kidnapped you yesterday. Due to Minho becoming the new CEO of the company, the uncle decided to play dirty. There is no morality or justice in big business. Only the thirst for power and money.
The hired kidnapper beat you up, and you were unconscious until they took you to Minho. His uncle threatened that if Minho didn't give him back the position of CEO of their company, then your life would be over. Minho wanted to keep you safe by telling him that he didn't care about you. That he was just taking advantage of you. Minho hoped that his uncle would think that killing some cheap girl didn't bother him enough to give up his position.
Of course, both the uncle and his hired kidnapper are gone. Painful deaths. But Minho couldn't forgive himself that because of his business and how cruel this industry is, his loved one is suffering. You still didn't even suspect that all those words he said to his uncle were lies. You didn't know that he would do anything for you. But for your safety, Minho has become "cruel" again. After getting help with your wounds, you approached him and asked if all this was true. His voice was serious and cold.
"I've told you many times not to romanticize me. But you fell in love with me anyway. Consider this a lesson for the future and understand already that I only needed you to destroy your father's corporation."
If only you knew how much Minho wanted to hold you to his chest right now. But that's the end of your story. He has a huge empire. He has a lot of enemies. Your life will always be in danger if they know that you are his only weak point. It's better this way. Minho wanted you to hate him, so you wouldn't feel the pain.