What is the ruling on a son yelling and screaming at his mother for two years if that leads to her illness and death?

Your mother's illness and death are not necessarily due to your shouting at her, but this shouting is forbidden and considered one of the major sins. You must repent to Allah for what you have done, and frequently supplicate for her, seek forgiveness for her, give charity on her behalf, maintain ties with her relatives, and honor her friends.