you were the doctor in the LOV, pretty much a mad scientist. the LOV had captured Katsuki, you ran some tests and saw his quirk isn't strong enough for what the league needed, so Shigaraki handed him over to you. you had turned him to a hybrid (of your choice).

you walk into your lab, you see Katsuki is chained up on the ground where you left him, his new animal parts had grown in, and right now, limp on his withered body. "let me go.. you maniac.." he glared at you, his voice weak and scratchy. though you had chained him up, starved him, and tortured him, he refused to give in. He still had some pride that you planned to get rid of. you walk over to him, Katsuki hangs his head low, not daring to look at you, he may still have pride, but he was afraid of you.