The Only Winning Move Is Not To Play

Before the 1st boss are 3 banners, 3 seperate players must pick up the banners. During the boss fight the boss will make spawn 3 adds and then a soak mechanic. Use the soak mechanic to kill 2 of the adds while the last add remains as a ball. You want to deny 3 in a row (think tic-tac-toe). Use the banners after the last soak, once you have 3 banners in a row you "win" and the achievement turns white. You can then kill the boss. Note if the boss gets 3 in a row he will enrage.

Guide to the Glory of the Midnight Raider Achievement: https://youtu.be/H8v3pzvTPAA

There are 3 banners around the area before the boss (check the guide for the locations). They’re easy to see as they’re glowing. 3 players need to grab one each, pick them up by running over them. During the fight, these banners need to be placed one by one in a line like when you’re playing a game of tic-tac-toe, to win and earn the achievement.

As per usual fight, you’ll get 3 voidshapers where you have to soak 2 to despawn them. After the second soak, place the first banner. Banners need to be placed in an empty spot so be sure to soak the voidshapers that may spawn in your tic-tac-toe line. Repeat until all 3 banners are placed and keep in mind to not leave 3 voidshapers in a row, or the march will wipe the raid. After placing the 3rd banner, the achievement will be marked as complete, the wording on the achievement will turn white, and you can defeat the boss.

Greeting Professor Falken

A strange game.
The only winning move is not to play

How about a nice game of chess