Fizz is doing way too much damage

For a champion that can't be touched because he can troll-poll away from any damage, Fizz should not be doing anywhere near as much damage as he is doing. He is one-shotting any squishy with just a single item , combine that with and he can't die, ever. Why should something that is unkillable get one-shot burst? That damage is way out of control and it needs to come down.