So, I want to use a character as an avatar that is hard to see in the full image. I thought about taking a screenshot, enlarging it, cropping it and then uploading it as an avatar, but then I read the rules about the avatar and it said that you can’t upload third-party images. Is there any way to solve this problem?

Sorry if it's a stupid question.

I don't think there's any way to crop an image for your avatar use.

No.

the closest you'll get to cropping your avatar is installing the userstyle esix cafe and pick between your pfp being a perfect circle or a rounded-off square

https://userstyles.world/style/3694/esix-caf