The Witcher 2: Assassins of Kings

This is is the last boss in the game (end of Chapter III). There are two "stages" to this fight. Each one requires some strategy, but as long as you dodge and utilize your oils and potions (this is honestly the only spot in the game where I would HIGHLY recommend using potions/oils), then this boss shouldn't be too much trouble. On Dark, this is obviously much harder, but the same sort of strategies will apply.

The first stage of the actual fight occurs right after you save Sile or let her die in the tower. You will be in the same room as this encounter with her after you have made your decision. The strategy for both stages basically amount to casting Quen (upgraded REALLY helps here), rolling up to the dragon's face, and then hitting it with a strong attack (), but only hit it like once or twice, because it will lunge or claw. On Easy or the other difficulties, you can get away with getting hit, but on Dark it's a one hit kill no matter what armor you have on, so always keep Quen active (other signs don't really do anything to the dragon).

In the second stage, the dragon will destroy the walls of the room, allowing you to climb to the top. The game thankfully checkpoints you here before you climb the rubble to the roof. In this area where it checkpoints you, you can also meditate, so take that time to drink potions that make you do more damage or anything else that may help you in combat. I'd also suggest coating your silver sword in an oil to make it do even more damage. When you get to the top, employ the same strategies of dodging and hitting with  and you'll do sizable damage (so long as you have a good silver sword; I personally used the "Superb Yellow Meteorite Sword" as it does a lot of damage and can be crafted by Bras of Ban Ard in Loc Muinne. He also sells the diagram.). The catch here is that the dragon will duck and circle around and swing his tail, which will pretty much always hit you, so make sure you have Quen. If it goes down, recast immediately. I recommend rolling to where the dragon is taking cover along the roof and then dodge away as this will bait a swing, but you will have a chance to dodge. When he flies up in the air he is either going to breathe fire or fly along the roof to hit you. You can dodge both of these, but the window to dodge is relatively small. After you whittle the monster's health down, a QTE will take place and Geralt will leap onto the dragon and steer it into a tree.

As for this achievement specifically, you're given a choice to kill the dragon after it's impaled or walk away, and you'll need to kill it. After selecting the option to put the dragon out of its misery, the achievement will unlock.

WARNING: - *Only applies to Iorveth's path* During the quest "The Spellbreaker" in Chapter III, you're given yet another choice: to rescue Triss or Phillipa. Rescuing Phillipa will void the achievement, to avoid spoiling too much about the quest.