The final bracelet is in the Valor Dungeon. This dungeon is on top of the castle of Pia Island. The dungeon has some difficult puzzles, but nothing more than you should be able to handle by this point in time. The hardest part is unlocking this dungeon. The necessary conditions:
-Collect All Truffles: To reach Pia Island, you need to collect all the truffles and trade them with Truffly.
-Collect All Medallions: To open the barrier in front of the dungeon, you need the most powerful bracelet (up to that point in time). In other words, you have to have bracelet 6.
In terms of the dungeon, there are some difficult enemies but nothing you haven't seen already. The boss is slightly different, but not bad either. It is:
3 Spider Split Monsters
The blue and green you have faced before. The blue is the weakest and splits into 4 blue spiders. The green is next strongest and splits into 4 greens. The gold is the strongest and splits into the 4 spider colors (brown, blue, green, and gold) as well as a red bull enemy. Additionally, there is timer of 7 minutes before you begin to take damage. You will be motoring in this fight.
In terms of strategy, the 3 will split right about the same time. Focus your attack on the blue spiders and blue monster. Try not to take out the others so the large monster doesn't reappear. Have the big guys on the field will impede your attacks since they will pursue you much closer than a spider. After that, take on the green and then finally the gold. The gold will reform without killing the bull, but you don't want to leave him. Try to eliminate him.
After winning, proceed to the next room and continue forward to the final bracelet and your achievement.