Alright this achievement isn’t as bad as I thought plus I figured out a easy method.
For the first phase just shoot and dodge then when his sword starts glowing that’s when the crystal’s start. Also in his second phase it will attack twice so be ready to dodge twice. To avoid the crystal’s use Strifes Y ability world ender it makes you invincible and you can’t take damage so use it once or twice then get ready to dodge. Once you get him down to a quarter health use your Rage which you are also invincible hope this helps.