Game Killer Achievement in Vampire Survivors

While the achievement description doesn't specify anymore (it originally did on Steam), this can't be earned until after you obtain the Randomazzo relic. Refer to Randomazzo (10G) for doing so.

This is one of the hardest achievements in the game.

Unlike the other normal stages, the final enemy (aka boss) doesn't show up in Cappella Magna until the 30 minute mark. Surviving until the 30 minute mark is much more challenging than other stages. The main issue is the appearance of the various forms of Death while you're playing this level. Green Death and Purple Death can each randomly show up and just chase after you. You can't damage them, from my experience, and instead just need to avoid them until they leave. Most problematic, however, is Blue Death, who creates an infinitely long damaging barrier below you, preventing you from going south at all. Blue Death continuously ascends, forcing you to constantly retreat north while still fighting enemies like normal. Unlike the others, Blue Death can and should be killed to get rid of the headache it causes. It unfortunately will always dodge you if you try to approach it though, so you're mainly forced to damage it with incidental contact from your weapons. It'll easily take a minute or two to kill it, but the best you can do is continue strengthening yourself so you can move up through enemies without issue while you wait for Blue Death to die.

Things get really intense over the final few minutes, where the screen is just full of boss-level enemies. I recommend the following build:
 

• Evolved Santa Water
• Evolved King Bible
• Evolved Axes
• Evolved Lightning Ring

Since your starting weapon likely isn't one of those four above, obviously get it to max level, but consider getting the Spinach instead of whatever would evolve your starting weapon.

For a sixth weapon, there is actually a trick you can use to get nine weapons instead of the max of six: if you've unlocked Glass Vizard (see Glass Vizard (5G)) and have enough money (total outside of your runs, not just within the run), you can wait until you have five weapons, then go to the Vizard and buy all four weapons he sells (Celestial Dusting, La Rumba, Cherry Bomb, and Cavello). Now you can do the normal evolutions above and also get these four weapons to level 8 too. Having nine weapons instead of six will make you far more powerful going into the final minutes of this stage.

Once you hit the 30 minute mark, you'll be transported to a new arena where you'll fight an amalgamation of all of the Death characters. The main challenge with this boss isn't the boss itself (it just throws scythes at you, which are pretty easy to dodge). The challenge are all of the column and rows of beams that can do significant damage to you if you stand in them. They also restrict your movement and arena space, making it harder to dodge the boss's attacks. By this point, you've gotten plenty of firepower, so all you should really be focusing on is dodging the beams and attacks from the boss, letting your weapons do their thing. It'll likely take a couple minutes, but eventually the boss will die, dropping the Great Gospel. Pick it up to unlock Great Gospel (20G) as well as this achievement.