Big Game Hunting! Trophy in Bloodstained: Curse of the Moon

One of the hardest trophies in the game, you must defeat a gauntlet of 9 bosses. IF you play it legit, anyway. From the title screen, select the Boss Rush mode. In this mode you have to defeat bosses from Stages 1 – 8, including both forms of Gremory.

You start off in a hub screen that you return to in between every boss. There are several items in here, but note that you can only use each item ONCE. If you collect secondary weapons, they will not re-spawn. Also note that no characters have a default secondary weapon, including Gebel's Metamorphosis.
 

You also have all four playable characters. If one dies, you return to the hub to continue. Boss Rush mode continues until all four player characters die or you return to the title screen. Your life does not refresh, so you must be cautious. There are two heart life drops in the hub, but they also do not respawn.

Some tips for clearing this mode:

• As you practice, try to master Miriam for her greater range.
• If you can, beat the first 3 or 4 bosses without getting hit, or at least as little as possible.
• Using Gebel against Bloodless is good. You can stand on the middle umbrella and hit her without getting hit, only avoiding her attacks.
• Using Alfred's Fire Scroll against Gremory's first form will really help reduce damage.
• On that note, you can swap characters with the Fire Scroll active, transferring the shield to other characters until it wears out.

If you're having difficulty there are some cheats you can implement and still earn the trophy.
(credit to ivory7777 and GameFAQs).

CHEATS

From the title screen, you can hold buttons on your controller when launching Boss Rush mode to implement a few changes.

The cheats are as follows:

Refreshed hub in between bosses, including health
Unlimited weapon energy
Zangetsu with all the Soul Arts
Nightmare difficulty bosses

So if you hold + + and press to enter Boss Rush, you will unlock Zangetsu with all his Soul Arts, unlimited weapon energy and a hub that refreshes every time you return to it.

The cheats do not disable the trophies.