Situation: The client like to know what’s the correct way to uninstall Microsoft SQL 2016 after uninstall Veeam backup software.
A: If I understand correctly you are trying to uninstall SQL 2016. I found the following Microsoft documentation that explains how to uninstall SQL 2016.
Uninstall SQL Server
https://docs.microsoft.com/en-us/sql/sql-server/install/uninstall-sql-server?view=sql-server-2016