The Star Shatterer trophy in Metaphor: ReFantazio is not unlocking for you because of a specific condition related to defeating the final boss, Destroyer Charadrius. Here are the detailed steps to ensure you complete the achievement:

1. Understand the Achievement Requirement:
– The Star Shatterer achievement requires you to defeat Destroyer Charadrius at full strength without weakening him by defeating any minibosses that appear when you destroy Melancholia Crystals.

2. Navigate to the Final Area:
– When you arrive at the final area, do not explore and avoid destroying any Melancholia Crystals. These crystals summon minibosses, which significantly weaken the final boss.

3. Avoid Destroying Melancholia Crystals:
– If you destroy a Melancholia Crystal, you will have to defeat a miniboss, which reduces the power of Destroyer Charadrius. This will prevent you from earning the Star Shatterer trophy.

4. Defeat Destroyer Charadrius at Full Strength:
– Proceed directly to the objective marker without engaging with any crystals. This ensures that Destroyer Charadrius remains at full power throughout the fight.

5. Tactics During the Fight:
– During the fight, be prepared to swap out party members if they are targeted by Destroyer Charadrius, as he may announce a specific race that shouldn’t exist, which could lead to their death.
– Use high agility and defensive strategies like dodging and buffing to maintain your party’s effectiveness. The Sublime Spoonful dish and specific archetype skills can also provide additional turns and protection.

6. Check for Bugged Trophies:
– If you have already defeated the final boss twice and the trophy still hasn’t unlocked, it might be a bugged issue.

By following these steps, you should be able to complete the Star Shatterer achievement in Metaphor: ReFantazio. If you continue to encounter issues, it may be worth checking for any updates or patches related to the game.