You counter him with champs that have lasers (
), and you attempt to only fight him when he's not near minions (E refreshes indefinitely if he has minions, which gives him more Q shots and faster Tornado charge ups). Melee champs also do pretty well as long as their skills are not projectiles.
If you are playing champs that are generally weak vs him, you try to either avoid him, or you at least try to get behind his wall (if he has no minions near him to E to, this is pretty strong. If he has minions he'll just E to the other side of his wall.
Basically the whole premise of a fight with Yasuo is to cast spells that originate AT HIM not TO HIM, and self originating skills that bring your character TO HIM.
For example,
Beats Yasuo while
doesn't because Karma's W originates at Yasuo so his only option to escape it is to flash/use minions to get far away. LB he can block with Wind Wall, because her tether originates at her and counts as a Projectile.
Other counters generally involve skills which are self originating like
Ults's which throw the champ at Yasuo. If you can knock up Yas it gives a pretty powerful window to erase him.
Basically, the name of the game with Yasuo is to "Catch the Wind." If you can catch him with effective cc that he can't block, he's dead. If your team is comprised of soft cc, of which only a few are Projectiles, he will walk all over you.
Now, you'll notice I mentioned
. Unlike Karma, She and Vel Koz have a skill classified as a Laser instead of a Projectile: Their ults. Lasers bypass his Wall. That does NOT mean Lux vs Yasuo is an easy lane. If you mess up, Yasuo will win. But it does mean you have a tool to finish him off if HE screws up (like turret diving you in enough proximity to Q him into a root, and follow up with Lux's Ult).
Just wins because of spammage, but if he sucks as a player, Yasuo will win the trade by building
and mitigating the "sometimes" Vel hits. If it' a Good, Vel Koz, he can win.
Another super strong counter is
if played correctly. Her R cannot be blocked, as it counts as a Laser, her W is a floor target spell, not a Projectile, and E counters knockups. You probably won't land Q's on initiate, but if you manage to R Yasuo with Morg and wait for the stun, you can Q him then to put him out of commission for 5 seconds, and he'll likely be dead or almost dead by then.