Brew an Awkward Potion using a Water Bottle and Nether Wart
Add a Fermented Spider Eye to the Awkward Potion to make a Potion of Harming
To make it stronger, add Glowstone Dust to create Potion of Harming II
To make it throwable, add Gunpowder to make a Splash Potion of Harming
To make it throwable and stronger, add Gunpowder to the Potion of Harming II to make a Splash Potion of Harming II