Item description:

Only one 5th floor boss kill left for completing all Frifle's challenges.

For Great Hall the last npc missing is Trorc, a merchant orc that you have to buy him any item when you encounter him in the Gungeon
and he will join the breach. Deactivate Rainbow mode or you won't be able to buy him anything and run gungeons normally until
you fin him since using the elevator didn't seem to spawn him.

All the other trophies are done in this save so try doing the accumulative stuff like clearing chambers and killing with chandelures,
minecarts and pits. If that doesn't pop them you have the other saves with the objective not done yet.