How many crimson biomes can be in one world?

[Throwhann]

I'm new to this game and am wondering how many corrupt zones can be in one world. I have zoned one crimson biome off, and am worried if there's more that will ruin my world.

[LT2483]

When you beat a certain boss and enter "Hardmode", it will send a V shape of crimson/corruption and another spreading biome throughout the world. Not only that, you basically need to break altars right after, which puts random blocks of crimson/corruption throughout the world each time.

In other words, the spreading biome your world starts with is the least of your issues and you shouldn't worry about it. You will get a tool to deal with it after progressing.

[Crawling Chaos]

In big worlds there usually are 3-4 "evil" biomes. But as LT2483 said, there is not much point in fighting the corruption (building pits/walls or cleansing it with purification powder) until a certain point in the game. But relatively soon after this point of the game you will be able to buy a powerful tool to fight the "evil" biome.

[stealthXG]

A lot if you don't keep under control. This only applies during hard mode though.