One time i played yi in a normals, i was 0/6 to a vi that was beating my butt invading me. I got 6 and i double killed her and the person who was with her.
Another i walked up to a full hp turret with no minions and killed it by myself. Only other champ ive seen do that is a ap Xin and thats because of the heal. Yi just pumped out that much damage.
He also has the highest pentakill rating of nearly every champ by a large margin.
He does not fit into team fights well, which is why he is not picked in worlds.
You can try to confuse the two but you will notice there is a hefty difference between team play and solo play.