My neighbor recently acquired a new puppy. They have it on a leash tied to a fence in their back yard. I am home most days and see that it never gets attention and doesn’t have space to walk around. At what point is negligence considered criminal?

Yes, is a crime. Call the police and report it.

I would call Animal control right away. That's a terrible thing for a dog to endure.

Some adoption groups in their paperwork forbid tethering an animal outside. If you can find out where it was adopted from you may be able to report them.

If they continue to keep the puppy tired up and neglected l would call animal control.

I'd call it in if I were you