Your not alone in your cat going bonkers when he goes to the Vet.
I have six and Two of mine are the same way. It takes me, a vet assist and sometimes the Vet to do anything with two of mine. Shadow my Maine Coon and Snuggles my Tabby mixed. But the other four are just angels when they go to the Vet. I think cats are like people, in that some don't like to go to the doctor and others adjust even if they don't want to go.
My Maine Coon, Shadow is a sweet gentle cat at home, But he will scratch, bite and meow loudly when he goes to the Vet: I always dread taking him to the Vet.
Mom of six babies (cats) Three (dogs