It's not the worst thing ever, but Kelt's extreme misogyny and degradation got really uncomfortable. Plus if I remember right, the farm owner gets pissed if you turn Kelt into Kelly. It's not one specific scene that makes him such a hateable and disgusting character, but rather all his smaller interactions together being so repulsive. At least you can still get back at him in a very ironic way which, in my disgustingly humble opinion, prevents him from being the worst character across the Fenverse games. He's still massive prick though.