Malice is an uncountable noun, meaning it refers to a general concept or quality rather than something that can be counted.
Think of it like this: you wouldn't say "three malicies", just like you wouldn't say "three sadness" or "three happiness".
If you want to express multiple instances of malice, you could use phrases like:
* Acts of malice
* Instances of malice
* Motivations driven by malice
* Signs of malice