The best diet for a cat begins with raw meat. Raw meat provides a concentrated form of protein that a cat can readily utilize. Don't worry that your cat will get sick from raw meat. They have evolved very strong stomach acids that destroy bacteria that would make a human sick. Meat contains high amounts of the amino acids cats must have.
Taurine is critical for cats.
Arginine, another amino acid found in meat protein, is also important for cats. Arginine is important for heart function, the pancreas, and for keeping the gut healthy, in addition to its detoxification role. Cats also need animal fat. Unlike humans, they must have animal fat as a source of fatty acid. Arachidonic acid is particularly important for feline immunity.