Cull for Scaling and extra Cut Down Damage
Sion's Skill Max Order: Q → W → E
Matchup Tip: If Sion Channels Q, Instantly E him to cancel it, which places it on a 2 second CD. If Sion charges Q for 1 second or longer, do not E him because he can cancel his Q while you're in mid-air and it will knock you up.
Level 1: Quinn E cancels Sion Q, so if he charges it, vault him and it will be cancelled. When you do this, he can Q again after 2 seconds so make sure to not take a long trade after you do this.
Level 2: Be careful behind minions to avoid Sion E. Move unpredictably so his E can't hit you.
Level 3: If Sion uses W, try to AA him as many times as you can to break it. If you break it before 3 seconds, the damage doesn't go off. I recommend to be in E range against Sion because when he uses Q, you want to be in vault range to instantly cancel it since you only have a 1 second window to cancel his Q before it knocks you up.
Level 6+: If Sion uses R, try not to get hit by it so it doesn't stun you. If he hits you with his R, try to use your E as quickly as possible to try to cancel his Q that he will be charging up.
Quinn's E actually CANCELS Sion's Q, but puts it on a 2 second CD. To play the matchup correctly, play back to dodge Sion E (just watch out for your minions and try to not stay in a straight line from Sion behind your minions so Sion will be unable to use his E on you).
Next, if Sion EVER charges Q, immediately vault him to cancel his Q, and then go for a quick PTA proc trade and back up before his Q comes back up (canceling his Q puts it on a VERY short 2 second CD, so don't be greedy).
99% of Sions don't know that you can do this, but after you do this mechanic a few times, the Sion's will start reactivating their Q quicker.
However, Sion's Q ONLY knocks you up if it's charged for at least 1 full second. So, you must vault Sion very quick to avoid being knocked up, because otherwise Sion will Q you mid vault if you wait too long and actually cancel your Vault, putting you in a dangerous position.
Post 6, your goal is to try to side step his R (quite hard to do, but it's really the only option).
If Sion lands his R on you, then don't panic. If his R was fully charged, you will be stunned for 1.75 seconds, but if the charge isn't for long, it goes 0.75 seconds (the duration is .75-1.75 depending on his charge time).
If he lands R on you and he isn't charging for long, then you are quite safe because Sion will use Q after, but if you're stunned for 0.75 seconds, then you can vault away from his Q after safely because Sion will be unable to channel his Q for 1+ seconds to knock you up.
TLDR, just don't get hit by Sion's fully charged R, If you hear that Sion sound, then RUN FORREST, RUN!!! Go Lord doms 3rd to pen his armour, when you have it then you beat sion up later on. (: