Thymesia

This is a real pain no way around it. However I found a cheap little trick that will definitely save a ton of time so that you don't have to play the whole tutorial over. This method is dashboarding!!

If you have a bad start or are about to die press start and close out of the game. When you get back into game you will respawn with full health right in front of boss room.

Now the best part is even if you do die (you will) instantly open menu and close game. It will respawn you in front of boss arena with 0 health. However with just a short run back you can refill health at beacon. The enemies wont repawn either. Much faster than playing whole tutorial.

Now for tips on the fight.

Parry parry parry. All his attacks can be parried. Stay close to him and continue to attack with RB. The only time you will be using RT is after successful parries, or when he does the jump attack. And holding RT attack is not worth it, takes too long and using his stolen weapon is too slow of an attack.

This still took me over an hour, but once you get the parry timing down it's not too bad. Finished with 2 health potions left.

GOOD LUCK!

If you like me can't parry the boss, here how I've done it:

Just run around the arena.
As soon as he start chasing you, he does two things: a big move with the sword upwards, or a horizontal slash followed by a slash to the ground. Both are really slow.

The second one is the move you can exploit: run away, wait for the big slash from above, charge in and hit him twice. Just be careful: the horizontal slash has a wide range and can actually hit you if you are too close.

Other than this, when he jump up, you can time the dash and get behind him for some free hit.

When he screams and slam the sword on the ground DODGE IT. It can hit you even if you think it's out of reach. You can hit him after this move too, but it's risky.

All other moves can be avoided just by running around and staying as far as you can.

Your base attack will chip at his maximum hp little by little, so It's safer to hit him with fast attacks. I managed to do it with 1 potion left, so there is room for mistakes.

IF you are out of potion or for whatever reason you feel like you are doomed, pause the game, go back to the menu and try again.
If the boss kill you, exiting on the dashboard won't help you (at least, didn't worked for me on my Xbox).

Good luck.

Varg is the first boss at the end of the tutorial. You are meant to die to progress the story, but to unlock this achievement you have to deplete his health bar once.
He hits hard and you will be dead after 2 hits. Luckily he only has very few move sets and all are easily learnt after seen a couple of times.

To defeat him simply just stand still, wait for his attacks and parry each with LB. (Timing is crucial as you have a very small window to parry the attacks, but after a few tries you'll get used to it.)

As soon as he finished with his combo, hit RT ONCE and then wait for his next attack. Don't be greedy!

Keep repeating this until his heath bar is empty. The achievement should unlock after the cutscene starts.

It is worth mentioning that if you die and the cutscene starts, the game moves on to chapter One and you'd have to start a new game and replay the tutorial to try again.
There is a workaround though.

Play through the tutorial until you get to the chair. Then kill the knight so he drops the Key to the Cemetery. Once you have that, go back to the chair to save your game.
Now close your game so your save uploads to the cloud. Now you have a backup save and you're ready to move on to the boss.
If you happen to die, as soon as the cutscene starts do the following.

Hit the Guide button > press Start on Thymesia > Manage game > Save data > your Gamertag > Delete from console > B until you're back on the Home > Start game again and load your save.

Depending on how fast you quit out either you should be back at chair or front of the boss room with 0 health in which case you can just run back to the chair to refill it.

Good luck!

P.S.: This is my first guide so any feedback would be appreciated.