Formal:
* Ne craignez pas: This is the most literal translation, meaning "Do not fear."
* N'ayez crainte: This translates to "Have no fear."
Informal:
* N'aie pas peur: This translates to "Don't be afraid," and is more casual.
Other options:
* Ayez courage: This translates to "Be courageous" and can be used as a way to encourage someone to overcome their fear.
* Ne vous inquiétez pas: This translates to "Don't worry," which can also be a way to reassure someone and calm their fears.
The best choice for you will depend on the situation and who you are speaking to.