The Potion of Harming in Minecraft isn't useful on its own, as drinking it will cause you to take immediate damage. However, when you turn one into a Splash Potion of Harming or Lingering Potion of Harming, it becomes a powerful weapon that you can use to gain an edge when fighting tough enemies.
How to Make a Potion of Damage! | Easy Minecraft Potion Guide
These are the ingredients you need if you want to make a potion of damage:
If you want to make your drink stronger, you will need:
If you want to actually make your drink useful, you'll also need the following: