Vampire Survivors

Each of the five normal stages (Stage 1 through Stage 5) has a boss that appears at the 25-minute mark. Once you survive that long, a bigger and much stronger enemy will show up. However, the boss itself, other than its size and HP, is no different than a normal enemy, really. They don't have any attacks or anything, so you'll just need to kite it around and avoid it until it finally dies from all of your attacks. It's easiest to just do tight circles around the boss to keep the horde at bay around you while you whittle down the boss's health.

Once it's dead, it'll drop a treasure chest, and you've essentially "beat" the level. Once you end the run, you'll unlock the achievement for beating the boss of that stage, and you'll unlock an achievement for unlocking a Hyper mode version of that stage. You'll need to do this for all five normal stages to unlock this achievement.

If you're struggling to accomplish this, obviously you'll want to first just get enough money from doing runs to upgrade all of your permanent stats between runs. During a run, by far the best three weapons are:
 

• Evolved Santa Water
• Evolved King Bible
• Evolved Axes

Just having those three evolved together will make you able to resist a significant amount of enemies. You should aim for those three weapon evolutions in every run of every stage. For your other three slots my recommendations are as follows:
 

• Evolved Lightning Ring - The best part about this is the Duplicator item you need to get to evolve it. The Duplicator adds extra projectiles for every weapon, making you significantly stronger
• Evolved Runetracer - This is ideal for narrow stages such as Inlaid Library and Gallo Tower, but not as great for others. It bounces off walls and explodes, so it's great with the nearby walls of those two levels, causing tons of explosions
• Song of Mana - If you don't want to evolve it because of the curse required to evolve it, at least consider its base form for verical levels, such as Dairy Plant, Gallo Tower, and Capella Magna. This one only shoots vertically, but it's quite strong when leveled up to level 8
• Spinach - If you aren't set on a fifth or sixth weapon, consider at least getting the Spinach item, as it'll add an extra 50% damage across the board when maxed out