Can a yasuo 1v5

Yes, unless the enemy team is fed too.

no he cant because every yasuo players are mentally retarded irl

Yeah. Many fighters can do so as well, but not as well as Yasuo in some cases.

Yes but only in the correct circumstances which should occur near never. Under the right situations theoretically any champion in the game can 1 v 5 but realistically it should not happen.

Against a specific teamcomp and a bad team that is spread out, yes. Against 5 people at once, never. He just gets stunlocked and instagibbed across the map.

Potentially, but he needs such specific circumstances (minion and champion positioning and rotations) that it won't happen 99.99%of the time

vs a team with very behind damage dealers, low cc/point click cc meaning they are using skillshot cc to cc him and they throw it into his windwall an he lands a Q knock up on both carrys/squishies and he has enough lifesteal to fight 3 low damage champions then yea he can.

Depends how many items he has, aka has he reached draintank status or not?

Not sure what 'generally balanced' is supposed to mean in this context.

Against a low damage team Yasuo will be able to 1v5 easily once he gets lifesteal.

Against a squishy team he can 1v5 if he gets a good ult.

If played well, yes. Depends on how much targeted damage/cc the enemy team has though.

If the enemy has little to no hard CC... yes. They just need to be somewhat damaged and string in a little.