Zed

He can easily one-shot you at any point of the game and can just W out of your cage. Due to his relatively high pick-rate, you should definitely ban him if you want to play Veigar.

Fizz

He can jump over your cage with his E, can dodge poke with E and Q and has insane engage and tower-dive abilities. Definitely not a nice matchup.

Katarina

She can E out of your cage almost anytime and can dodge your other abilities as well.

Ezreal

He can just E out of your cage and can deal consistent high damage to poke you to death.

Kassadin

Kassa can R out of your cage almost everytime after he hits lvl 6. Late he is one of the few champs that are able to almost outscale veigar and he can one-hit you late easily.

Talon

He can just one-shot you easily early- to mid-game, if you dont have your cage up.

LeBlanc

She can just tp out of your cage,

Akali

Has some dashes to dodge your abilities and can one-shot you most of the time.

Xerath

He outranges you by far and can easily prevent you from getting stacks.

Morgana

Both as supp and mid a threat for Veigar. She can just E herself to ignore your cage and make it a lot harder to get your combo out.

Blitzcrank

You are dead if he lands a hook while someone with some damage is near him.

Nautilus

Just another hook supporter.

Leona