Formal:
* District Attorney (DA): Used in many US jurisdictions.
* State Attorney: Also used in some US jurisdictions.
* Crown Prosecutor: Used in some Commonwealth countries.
* Attorney General: The chief legal officer of a state or country.
* Solicitor General: A lawyer in a government department responsible for legal matters.
* Public Prosecutor: A more general term used in some countries.
Informal:
* Accuser
* Indictor
* Plaintiff (in civil cases)
* Persecutor (often used figuratively, implying unfairness)
More Specific:
* Special Prosecutor: Appointed to investigate a specific case or issue.
* Lead Prosecutor: The main attorney responsible for the prosecution in a case.
The best word to use depends on the specific situation and the desired tone.