Here is the instructions on how to uninstall SQL Server.
1Stop SQL Server related services
Type services.msc in the search box and press enter.
Find all the services related to SQL Server, and stop these services.
2Uninstall SQL Server from Control Panel
Go to Control Panel and click " Uninstall a program ".
Right-click "Microsoft SQL Server 2014 (64-bit)". Click Uninstall.
Choose the instance which needs to be uninstalled. Click Next.
Click Select all, and click Next.
When all the features have been successfully uninstalled, click Close.
Uninstall all remaining SQL server related programs in Control Panel.
3Delete SQL Server related files
3.1Delete SQL Server related folders
Delete the default installation folder of SQL Server.
When all the steps are completed, you have successfully uninstalled SQL Server.