SMITE

Here's how to get this legit:

1.) Play Siege mode. The reason for this is that it had a nice, compact Jungle (aka, central area) you can hide in, while having easy access to the two lanes on the left and right.

2.) Pick an assassin class (I liker Thor myself for this).

3.) Before the game starts , rank up an ability that gives you high damage, but preferably not too much of a skill-shot (i.e. Thor's Berserker Barrage, where you do high damage while spinning around, is excellent for this)

3.) Now, go to the center of the map and wait. Hopefully, eventually, you'll see a one-on-one fight in one of the lanes. When you do, wait for the enemy to go down to about 50-60% health -- this is your time to strike.

4.) Run toward that fight, but be sure to exit the Jungle behind the enemy, so you cut off their escape (and so they don't see you coming.). Now hit them with your high-damage ability. You'll most likely land this attack as they shouldn't have seen you come into the fight.

5.) Finish off the enemy if they're not dead already. Hopefully, this is the first kill of the match.

6.) Repeat until achievement unlocked.

(One last note -- remember, like with all other achievements in this game, you have to be playing in a PvP match. Co-op matches against the computer don't count).