Im sorry, that's so sad. I have had that happen before. Did it hatch slow, like it took a while. That can weaken the chicks and/or cause deformity. Looking at legs and feet he doesn't have much of a chance of survival. He will probably not walk and he will just be suffering. He should have already been up and running. Chickens are sometimes a difficult animal especially when young. It can be very hard. I'm so sorry.