No crime. A hollow is not sent to hell for any crime. Most people become hollows because of despair, sadness and those kind of emotions. When a Shinigami defeats a Hollow their Zanpakuto cleanses them of any crime or evil they did as a hollow. The only hollows that go to Hell are those who were evil and did crimes when they were still living humans. The only example we have of this is Shrieker, who was a murderer when he was alive.