Xexyz/YMMV

Anticlimax Boss: Garuza Palace: it may hit hard and fire fast, but it always fires directly at the players. This comes at a part of the game where the player can freely move in all directions, making these shots far easier to dodge than it may sound. It's not the easiest boss in the world, but anyone who makes it that far is unlikely to lose to it.
That One Boss: Horrza, the Area 9 boss. Also qualifies as Bullet Hell. Lampshaded in-game when an NPC tells you "The enemy boss in this area is VERY TOUGH! Be careful."