What moves or tactics are best against Yun to counter hit him from his godlike blockstrings?
Patience probably isn’t the best answer, but in terms of divekick pressure on wakeup, try to mix up delayed wakeup with regular to mess up their timing. If you get up early, try and use jab or focus attack to get back to a neutral position without getting stuck in another blockstring (hat tip to Tenchi for that one)
As for when you’re in a blockstring, nothing you can do except be patient and wait for the right moment. Options for when that moment comes could be a focus/backdash, EX Criminal Upper, EX Zonk, or cr. LK -> MK Ruffian, although the last one is pretty risky.
@Rytor Appreciate the shout out.
Just as a bit more information; You can anti-air Yuns dive kick with Focus Attack pretty easily.
Also, a lot of Yuns like to end block strings with his shoulder attack. Most people do it after a standing MP or crouching MK. If they have this tendency you can hit focus attack inbetween the block string and make them a little more honest.
An impatient Yun will use EX-Lunge Punch to get in. You can use regular Zonk on reaction to punish that so be sure to stand a distance out and see what he favors. Dive Kick or Lunge Punch? Then attack accordingly.
Be patient. Yun has low health and you can make a comeback pretty quickly.
Anti airing Yun isn’t easy. Focus attack is one of the better options for anti air. C.mk is also good to make dive kick whiff. Don’t forget bad sand. It’s usually decent against dive kick characters.
Anti Airing Yun is rather easy. The problem is once you miss an AA he’s in your face and pressuring you.
s.LP, jumpback j.LP, s.MP, s.HP, cr.HP, s.HK (risky but if you see it go for it.) knife jumpback j.LP, knife cr.HP, knife s.HP, cr.MK, HK ruffian…
more than enough options for all ranges of divekick.
Doing neutral jumps during the neutral game will cause Yun to be more carefull with their divekick attempt, also focusing against Yun his divekicks is great, especially focus attacks that move forward during their charge, causes the divekick to hit higher and more likely to get a lvl 2 crumple. Don’t charge too long though, a simple lvl 1 is fine because if you charge too long Yun can do upkicks, backdash or even Ultra. If you have good reactions you can challenge Yun by jumping forward or backward with an attack. jumping lp is great as it has fast startup, long active frames and great angle, other attacks like j.mk are good too.
Try to block divekicks standing to give Yun the least amount of advantage, you can challenge him after it with an EX criminal, EX zonk, throw or even cr.lk/lp. This will take practice though as you will also have to recognize how good the divekick is placed. The crossup divekicks that are blocked standing are the most disadvantageous for Yun unless they are done during your wakeup, them they can still have big advantage.
Cr.mk might get crossupped with a divekick if you are doing it too close, so be aware of that. As for badspray, don’t try to do this after an upkicks knockdown, 2 things can happen, The yun can start with a meaty attack which will beat the badspray, or he does a crossup divekick which the badspray won’t hit. It will only hit the divekicks which land in front and which aren’t timed properly, which no decent Yun player will do.
Doing neutral jumps during the neutral game will cause Yun to be more carefull with their divekick attempt, also focusing against Yun his divekicks is great, especially focus attacks that move forward during their charge, causes the divekick to hit higher and more likely to get a lvl 2 crumple. Don’t charge too long though, a simple lvl 1 is fine because if you charge too long Yun can do upkicks, backdash or even Ultra.
The best time to do a badspray is after an OS light lungepunch and a raw lungepunch. These lungepunches will generally hit with their later frames and cause the opponent to be further away and won’t allow Yun to do a crossup divekick or they have to walk forward a good bit to do their cr.lk/ (cl.)st.lp OS.
Medium lungepunch is the one that will be comboed into and will leave him close enough for his shenanigans.
*However if Yun will dash after ANY lungepunch the badspray will beat any grounded normals or jump attempts! So keep an eye out for that.
As for blockstrings, unfortunately for Cody he can’t do a whole lot about that unless you take a big risk. Yun his blockstrings consist of fast normals, chains and build in frametraps. Cr.lk/lp, cl.lp is the go to chain for an OS and hitconfirm, after this he might mix it up with a throw, (EX) command throw, divekick, extended chains, frametrap etc. Might want to try to challenge with an EX criminal/EX zonk here. Be on the lookout for cr.mk and st.mp they most likely will be cancelled into a shoulder which you can interrupt with a lvl1 focus, or ex zonk. If you crouchtech with cr.mp or cr.hp you can stop another divekick attempt, but you are susceptible to frametraps.
Now for the annoying shoulder pressure. Try to stand block these because if you keep crouching Yun is constantly in range for another st.mp. This way if it st.mp misses you can whiff punish it.
This sequence is very annoying as some mindgames will come into play. On hit Yun can keep pressing his offense, he can press another st.mp, he can dasdh forward if you are afraid to get counterhit, and if you are not paying attention even doing a regular jump in or divekick. If Yun keeps abusing st.mp xx shoulder on hit you can get a counterhit focus crumple after he does another st.mp and interrupt the shoulder. Regular or EX Zonk are good challnges also as they will go under st.mp.
On block you can challenge with normals, cr.lk has enough range and you might want to cancel it into a (light)criminal upper. st.hp will counterhit Yun, and also stop Yun from jumping. St.hk will miss if Yun is too close.
Yun also has the option to wait and try to whiff punish you attempt like st.hp, so cr.lk might be the safer option.
It is a tough matchup and you want to be pro active in this match and take away any advantage he has. Stopping his divekicks is a big thing as he then has play the ground game.
Yo !
I found this yesterday :
I hope this will help you, enjoy ! 
sweet, thanks all.