A Casual Master Yi One-Shot Build

With a Q-AA-Hydra, the build on average hits for 1944 damage.

If neither Q nor AA crit, it hits for 1424 (4%) If Q crits but AA does not, it hits for 1668 (16%) If Q does not crit but AA does, it hits for 1830 (16%) If both Q and AA crit, it hits for 2074 (64%)

This was calculated via comparing every item Yi could possibly build and their cost effectiveness in contributing to his Burst Damage. The target in question was assumed to have 2000 HP, 85 Armor, and 30 Magic Resist (the average-ish stats of a squishy champ). Ignoring any defensive bonuses from their abilities, this means that this build has a 64% chance of one shotting any Marksman and most other squishy champs in the game. Even in the off chance it doesn't one shot the enemy champion, Yi has more than enough Attack Speed to give virtually anyone squishy a run for their money in terms of dying immediately afterwards anyway.

This also takes no account of Runes or Masteries.

Build's derp but hey, maybe a Yi player out there will have fun killing squishies literally instantaneously.