Dead by Daylight

In order to unlock this achievement, you will need to use The Oni's three perks: Zanshin Tactics, Blood Echo, and Nemesis. Zanshin Tactics allows you to see pallets and windows, allowing you to better predict where a survivor might run towards. Blood Echo will be extremely useful if you hook a survivor while their teammates are injured, as it applies Exhaustion and Hemorrhage status effects to those still running around. Lastly, Nemesis applies the Oblivious status effect to any survivors who stun you for forty seconds, which can be helpful if you are on a closed map such as The Game and they can't base your proximity on terror radius.

The best way to achieve this in a match is to make sure you are damaging generators (Gatekeeper), chasing and downing survivors quickly (Chaser), hooking all four survivors three times preferably to maximize sacrifice points (Devout), and making good use of Blood Fury and/or the Demon Dash ability (Malicious). Any sufficient combination of these four will increase your emblem score, which in turn will grant you the "Merciless Victory" result you desire.

On a personal note, I tend to do these achievements with just the three perks needed, no offering, two add-ons however I like. For some reason, I think these mess with my outcome, so I just leave them off. Just figured I would give you all my specific way of gaining these achievements.

Note: Yes, this is a guide for an achievement the poster has not unlocked, but if you look through my DBD record, I have every adept from base game and only ones I haven't gotten are the more recent releases such as this. Will be going for this later this week. Good luck all!