Note that the most damage Link can ever deal in a single hit is 3.
Standard Sword deals base damage of 1. It can be upgraded by one via various means like Piece of Power, Red Tunic, Spin attacks and Dash Attacks. Note that none of these stack and the most damage that you can ever do with the standard sword is 2. Similarly the Koholint Sword has a base damage of 2 and the most damage you can ever do with it is 3.
*Pol's Voice instantly dies to pots being thrown at it.
**Lots of enemies have a resistance to arrows, such as Wizzrobes (2 arrows to kill despite having 2 health) and Pol's Voices (4 arrows to kill despite having 4 health).
***The Boomerang is a weird case, where it will one-shot plenty of enemies while only doing 1 damage to others. Notably the only item that can kill Sparks.
Positioning an enemy on Link's left side (near his sword-hand when holding a spin charge) lets you hit it twice with one spin slash. This is useful for many boss quick-kills, such as on Genie and Ganon.