Bound by Flame

This achievement is for maxing out the Warrior skill class.

You get 2 skill points per level and to max out each Skill Tree you will need 36 skill points total.
The first time you rank up you will hit level 2 so that means you must reach level 19 in order to acquire enough points.

You will not be able to max out more than 1 skill tree per playthrough so you will either have to do 3 separate playthroughs until level 19 each dedicated to one skill class

OR...

You can save all your points until you hit level 19 then make a save file and max out each tree while reverting to your save after each is maxed.

This is easier said than done, even though the game is fairly easy on the easiest difficulty you can find yourself getting killed quite frequently if you do not know what you are doing.

So I recommend you get used to the game before trying this and play on Recruit.

Also you get "Feat" points, 1 per level gained, which you should use to buy the 2 experience boosts BEFORE anything else, Practical - 10% for 1 point & Passionate - 20% 3 points.
- you will need to eliminate a certain amount of enemies to unlock each one.
These feats will help you get to level 19 faster.

Be sure to do as many side quests as you can to help get exp.

If you are having trouble fighting enemies you could spend a few points - like in the Warrior class for health regeneration and/or improved parrying which will help in the beginning.
- Just remember that each skill point used will have to be earned back by leveling up another level so do not get carried away if you are going to use this method.

As with and the earliest you can unlock this achievement is at level 19 if you put all your points in this tree. It is not possible to reset your skills and you will only be able to fully unlock one tree per playthrough through normal play. It may be possible to grind out more than on tree but with the unusual respawns I wouldn't recommend trying.