First you need a mod for the sticky grenade. You can wait until you find this mod automatically or you can just buy it at an ammo dump vending machine (green vending machines).
Kill enemies with a single sticky grenade
In Borderlands 3 there are some trophies and achievements you can unlock. To complete the game with 100% you have to master all the trophies or achievements successfully. To make it easier for you, we would like to explain the following trophy to you in this guide:
The easiest way to kill two enemies is to go to Pandora, the Droughts. Then find some Level 1 enemies and throw the grenade at them. Both enemies must be killed at the same time.