EXTRA: Seal III Achievement in Vampire Survivors

This can easily be done with Sigma on any map, but you can speed it up by turning on Hyper and Hurry so enemies come at your fast. Playing with Sigma starts you with 118 Banishes. I first recommend getting at least four or five weapons and accessories so you're good to mow down enemies, but just make sure you don't pick a sixth weapon nor a sixth accessory. Then, once you have most of a build, just start banishing a weapon or accessory every time you level up. There isn't a direct way to track how many you banished during a run, but you can just watch your 118 Banishes go down to 78 to know you've banished 40 things, then quit the run to unlock this achievement.

As a side note, if you have five weapons and five accessories equipped, you will run out of new stuff before reaching 78 Banishes remaining. Fear not. You can still banish equipped stuff too. You won't be able to level it anymore after banishing, but it'll still count for this achievement.