Pyke has several nerfs on the PBE specifically targeted at reducing his power in the midlane. He'll have less waveclear, less MR, and a lower execute threshold at higher ranks.
Everything that Pyke does to you is a telegraphed skillshot. You are given every opportunity to juke, dash, or Flash away from his entire kit. Bob and weave from side to side so he has trouble lining up a hook.
He is an incredibly squishy AD assassin that doesn't have the damage to 100-0 people on his own unless he gets super-fed. He cannot build health. He is discouraged from building anything but lethality. Hit him with CC and focus him down, just like you would with any other assassin.
Area denial abilities like Soraka's silence or Veigar's cage are a death sentence to Pyke. If you restrict him from getting in, or getting out, he can literally do nothing in a teamfight until his teammates get someone low enough to ult.
In the laning phase, bully his carry, not Pyke. Pyke will just regen through poke for days, but his cooldowns are hella long early on and he doesn't have the damage to 1v2, or even 1v1. If you attack the carry and get that health advantage, Pyke will lose trades. Think of him like a jungler that is permanently ganking: he can only snowball a winning lane, not save a losing one. If you shove him into tower, Pyke cannot hook you through the wall of minions and needs to use his cooldowns to clear (i.e., not use them on you). Since they are so long at early ranks, he can't do anything useful if you keep shoving him into tower.
You beat Pyke by being a better player than him. Buy control wards to warn your teammates against his roams, dodge his skillshots, and control the wave. Pyke feels strong at lower ranks because no one is doing that.
why is pyke mid a thing?
why is pyke the support --- ad evelynn
why does pykes ult reset?
Why does pyke need all that grey health. 
What is pykes weakness?----- 3 champs focusing him'
Outside of a 2v1 what characters actually get to turn on pyke?
is it lucian ? because everyone else seems pretty useless
Oh besides top laners
or 
) as he literally cannot build against it. Give him a round of good CC and he crumbles with a little bit of focus.