Best thing to do, is force him to expend his CD's..
Glass cannon fizz counter: Buy a QSS, cleanse his ult, and procede to use him as a mop.
AD fizz counter : Force him into a fight he cannot win, with this he will try to escape.. Wait for him to burn his escape, CC him, exhaust, Even use flash to catch him up, then procede to kill him.
So yea, the ultimate counter to fizz ? Buy QSS, Makes him useless as a glass cannon, and if you force him to expand his CD's "Befor" you unload your CC on him, he is as good as dead..
Like most people are like "QQ FIZZ JUMPED AWAY AND I COULDNT KILL HIM" --> Simple solution, "Wait untill he escapes" to use your CC, do not unload everything on a fizz @ the start of the fight unless you have CC to spare... Ultimate counter to fizz ? Ezreal..
Its useless unloading all your stuns, ignites, exhausts @ the start of the fight on fizz, unless you can 100% secure the kill, otherwise he will just bounce away, and you wasted everything, why he just waits 10s for a CD, your waiting 120s+ for ignites, exhausts, flash, ultimates.