There are many classic traditional interactive achievements in "Monster Hunter: The Wilderness", and Assassin Hunter Achievement is one of them. To achieve Assassin Hunter Achievement, you must first go around behind the back and use a surprise attack without the monster discovering you, and there will be a button prompt.
How to do Monster Hunter Wild Assassin Hunter Achievement
Assassin Hunter
Proof of the First Successful Accident Attack
Go around behind the back and use the Accident Attack without the monster finding you, there will be a button prompt. Squatting can be triggered if you are not found to be approaching, turning areas, or wearing invisible clothes.