In this guide, you will find how to complete the Hunting Grounds trial in Horizon Forbidden West. You have to follow the simple steps below to complete it.
You will need a frost weapon to do frost damage, and you also want some tear damage. Hit the enemy with the frost arrows, and once the frost is full, you have to shoot the big sack off their back. You can use any tear weapon or normal arrows here.
Just follow the same steps to knock them down, and it will complete your trial.