Statement:
The level of criminal activities is lower in Tunisia than in South Africa

In the The Most Criminal Countries rating Tunisia holds position #79 ²⁰²² out of 139 and South Africa is #4 out of 139 ²⁰²².
Position of Tunisia is better than position of South Africa.
South Africa is leader of the "The Most Criminal Countries" rating. So it is wise to avoid visiting the country or, at least, you need to take additional actions to protect your life and belongings, compared to Tunisia

Referencies:

1. The Most Criminal Countries ²⁰²² by Numbeo

   The countries in the rating sorted by 'Crime Index' in descending order.

   South Africa	'Crime Index' value is	75.37
   Tunisia	'Crime Index' value is	43.94