Assuming he has his 2 crit items so he kills you in 2 attacks. 3 scenarios:
1. You are farming alone at tower-ish, but you have no minions by you he can use to dash to you right now, but he has more movespeed than you and tried to go the right angle to catch you.
2. like 1, but he has your minions to dash with.
3. you have a team mate or 2 with you, but not one that can 1v1 Yasuo.
4. (bonus) you are basically %%%%ed by not being close to any allied tower, you have no team mates that can cc him or kill him, and he has minions en masse for his dash.
I have been in all 4 scenarios and I die 90% of the time. why? He always gets his dash on me one way or another, and/or he uses windwall rendering me useless unless I go into his face, and, well, die. So is there anything other than chilling in base, guarded by platform turret, when the yasuo is loose?