To unlock this achievement, you need to score 180 points in one darts game.
Firstly, you will need to find a place that offers the activity, such as the place Steinway Beer Garden in Dukes or Lucky Winkle in Algonquin. Once you find one, you can just play with a random NPC, there is no need for a friend for this achievement. The easiest way to hit 180 points is to hit a red section that is under the 20, make use of the
button, this makes the dart steady, it will help you line it up. Be aware, this lasts for around 1 second only. Move your default crosshair up to the area and use the ability to steady the dart and throw it. Repeat this 3 times and you unlock this achievement. If you miss then leave and start up a new match with an NPC or try again later with a friend.
Here is a video guide.
Credit: hEx