This is pretty straightforward. Once you have used all Focus Attacks, the achievement unlocks right away. Keep in mind that you have to upgrade your Focus Bar at the shrines for 250XP and you need to buy this 4 times = 1000XP total because the Thigh Cut Focus requires 3 Focus Bars.
There are 8 Focus Attacks in total:
Eye Strike:
Unlocked automatically from the beginning.
360 Swing:
This needs to be bought from the Skills Menu for 500XP (costs 2 Focus Bars)
Strong Sweep:
This needs to be bought from the Skills Menu for 500XP
Face Smash:
This needs to be bought from the Skills Menu for 500XP (Max age to unlock: 59, costs 2 Focus Bars)
Double Palm:
This needs to be bought from the Skills Menu for 500XP (Max age to unlock: 49, costs 2 Focus Bars)
Vertical Strikes:
This needs to be bought from the Skills Menu for 500XP (Max age to unlock: 39, costs 2 Focus Bars)
Thigh Cut:
This needs to be bought from the Skills Menu for 500XP (Max age to unlock: 29, costs 3 Focus Bars)
Calbot Focus:
This needs to be bought from the Skills Menu for 500XP (You need to unlock this move first by collecting the mask on Mission 3 “The Museum”. When you first reach the fourth floor, turn to your right and go through both black gates. After that go down the stairs to floor 3 and turn to your right and you will see a blue-haired lady watching a mask, defeat her to grab the mask).