Who are the biggest velkoz counters (mid)

Velkoz counters most mages with his range, and is countered by Assassins with their mobility+burst.

Like the other comment Vel counters all mages , but gets countered by assassins , but even against assassins he is a decnt pick

A decent Diana is gonna absolutely dump on him if he doesn't rush RoA, and even if he does she's still going to be a big problem for him, just won't delete him in one burst.

I'd imagine a decent Zed is a nightmare.

Possibly Talon? A good Kat would be impossible to hit with most of Vel's kit. Basically champs that can either reposition so well that he can't hit them, or champs that can just hard All-in and blow him up.

Everyone, pretty much. Not that he's actually countered by everyone, but every other long-range mage can do his job better. They all have better CC, better hitboxes, and quicker burst. His True Damage was good back before the Tank Update, but now it's not necessary.

With that in mind, anyone who counters Lux, Brand, or Xerath counters Vel'koz even harder since his only hard CC is his E and it's shorter than any of theirs. (excluding Lux, since hers is a root, but it does serve its purpose better than his)

A good vel koz player will do well even when countered due to his decent waveclear, he can stop the enemy laner from roaming and sit under turret where it will be hard for him to be dove with

I've done well vs him as zed, but his waveclear early is terrible. He (Vel) may have a lot of poke for minimal mana usage which is why some ppl have been taking him as a support but he can't really do anything if you get behind him while he's ulting. But as of the most recent patch according to a certain site the current counters are supposedly: Pyke - Xerath - Fiddlesticks as the ''support'' counters. Corki Kassadin Vlad Katarina Zoe Diana Qiyana Ahri are the mid counters. But if you aren't skilled on them... you're really only countering yourself by overthinking it.

Jon Jones, king of eye pokes

Any melee/burst + Predator.

I would think Kassadin has to be a natural counter. He has mobility, ghost to dodge Vel's W and E while using minions to block Q, and can stop Vel's ult with is Q.

I never ever lost to a VK as Kat.