Divinity: Original Sin 2 - Definitive Edition (UP)

I didn't get this achievement on my first playthrough. I believe it doesn't pop it you give Almira the pieces to craft it. There are other ways to craft the swornbreaker but below is how I did it

The related quests are 1.) Unlikely Lovers, 2.) Almira's Request, and 3.) The Key to Freedom. The first one is found in the Reaper's Coast at x:705 y:323 complete that and Almira will ask you for help. Complete that quest and then sail to the nameless isles. Speak to Almira on the boat there and tell her you will craft the swornbreaker, she should give you the tablet back. You can read it at this point to get the crafting recipe, so it can be found easily in the crafting menu.

One of the pieces is inside the Arena of the Ages, which is inside The Academy of the Seven. The coordinates for them are: Academy x:346 y:823 and inside the portal to the Arena is x:618 y:600. You can take it from the arena boss' corpse. (There is a puzzle to enter the Academy, if the camera is pointed north, clockwise starting at the south east pedestal it goes sun moon moon sun sun moon moon.)

The second is in the Sallow man's chest coordinates x:122 y:204 (which is inside the cave at x:278 y:806). There is a tough troll guarding the cave and then the hidden door inside the cave. One way to get by the door is by dropping Alexander's head into the altar there. There is a potential boss fight and some locked doors to get through.

It can be craft easily in the craft menu (located in weapons) or by combining the haft, blade, and tablet.