How to uninstall .vsix Visual Studio Extensions?

In the menu, go to:

• Visual Studio 2017: Tools > Extensions And Updates
• Visual Studio 2019: Extensions > Manage Extensions

A new window will pop up, then in the panel to the left, click the arrow besides Installed to bring it down and select the menu item All.

All you have to do now is to navigate in the middle panel to your installed exstension, select it and click Uninstall.

To expand on the answer from @Brukvoyed, you can use the VSIXInstaller.exe utility to uninstall a vsix, but you need the vsixid to do so. To get the vsixid of a .vsix file, make a copy of the .vsix file and rename it to .zip. You can then open it and find an extension.vsixmanifest file inside. This is an XML file, and if you open it you will see an <Identity Id="guid"... /> node. The guid is the vsixid you use in the VSIXInstaller.exe command, like this:

vsixinstaller /u:12345678-1234-5678-1234-123456780000

In case Visual Studio does not start or cannot display the Extensions And Updates management window you may try to uninstall the extension from the command line. Use the VSIXInstaller.exe utility from standard VIsual Studio package.