here's yasuo's AD at level 9: 81.6
81.6 +
(80) = 161.6
yasuo's passive reduces his crit multiplyer to 1.8 , infinity edge apparently stacks additively instead of multiplied, at least if the wiki's information is correct, 1.8 + 0.225(infinity edge on yasuo) = 2.025
161.6 * 2.025 = 326.025 before any runes or other effects increase his AD further...
if yasuo were facing himself, he would deal 100/152.9 X 326.025 = 213.2
for his Q, you get 1.825 crit multiplyer and add up to 120 damage (which you would have by 9), this comes to 281.6 * 1.825 = 513.92 * 100/152.9 = 336.115 or 336 before any other runes and effects
let's say he's facing Lissandra since she's the most defensive mage
at level 9, she has 45.2 armor before any additional effects or items such as the components of zhonyas
100/145.2 * auto attack = 224.53 or roughly 225
same * Q = 353.9
with these factors alone, yasuo's kill time is roughly 2.9 seconds or less upon reaching his target
factoring in runes and static shiv, that number drops quickly...
then you get into stuff like building rod of ages or rylais, different matchups, etc.
all while being free to build more offense, bruiser, or even tank
is a good choice with 80 AD and 30% reduction of burst damage, but he's free to build pretty much whatever he wants because his core items have already been finished with only 6000 gold