Assassin's Creed Origins

This is obtained in the gladiator arenas (unlocked automatically via progressing in the story). Every section of the arena has three fights that consists of 3 waves and then a boss at the fourth fight. For this achievement, wait until the boss’s health is reasonably low (you’ll fill up your adrenaline meter without even trying due to hitting the boss and getting hit) and then press and at the same time to unleash a brutal unblockable overpower attack that should kill them easily. Upon doing this in any arena challenge, the achievement will unlock.