The Potion of Harming (Instant Damage) inflicts immediate damage to entities upon use. Crafted using a Potion of Poison or Potion of Healing with a fermented spider eye, it reduces health points when thrown as a splash potion or consumed directly. This concoction is particularly effective against undead mobs, such as zombies and skeletons, where it paradoxically acts as a healing agent due to their inverse reaction to potions.
The numerical item ID for Potion of Harming (Instant Damage) is 373
Numerical item IDs will only work in Minecraft versions below 1.13.
The item ID for Potion of Harming (Instant Damage) is minecraft:potion
This is the spawn command to give yourself Potion of Harming (Instant Damage) in Minecraft which includes the Minecraft /give command. If you are using the Essentials plugin you will need to use /minecraft:give instead of /give