Ok, so this one isn’t as bad as you think. in order to get this one, you need to master all 5 schools. When you first start the game, the style you first pick will automatically be mastered 👍
I give credit for the schools from Infamous solution for the grandmaster achievement, he listed all the schools there, but I’ll post them here to make things easier.
Forsaken School - #25560 (also includes calbot)
Kahlt Method School - #25563
Windfall School - #25566
Stagger School - #25568
Faejin School - #25570
To actually master the moves, you must first go to the combat trials and equip the move from the school you wish to master, then you have to use the right stick and dodge the incoming attacks almost perfectly. It can be a pain in the butt at times but if you find a good sparing partner, this achievement can easily be done in 1-2 hours per person 👍
Good luck everyone! Hope this helps y’all out and happy hunting!
Btw wanted to shout out my buddy/sparing partner XxIKINGJxX for helping me research this achievement 👍