Registering kills in Misty Woods

[Jeffaffah]

Hello fellow players of the game "Blade and Soul".

 

I have a slight question. How do kills get registered on the "Merciless" achievement? I seem to struggle finding out how it adds up.

• I have engaged upon a player(s), but after killing them with a group of others, I get little/close to none of the ones I engaged upon.
• I dealt the majority of the damage to a single target, yet the kill did not count for the tally.
• I dealt the final death blow to my target(s), but the tally does not increase.

 

So, how exactly does this work? If it's not (necessarily) the first engage, not the most damage, or the last hit, then how does it register the kill?