How to unzip a zip file to a folder but avoid duplicate folders?

What you need is exactly Bandizip by Bandisoft.

In Bandizip's settings, select the Context Menu heading. Then, under Extraction Menu, enable Extract Automatically.

If you like, you can even enable the Extract Automatically functionality as the default double-click action by selecting Extract Automatically in the Double-click Action section of that same settings page.

When you use Bandizip's Extract Automatically functionality, it will create a subfolder only when one is needed. If the zip file only contains a single file or subfolder, it will not create a subfolder. If the zip file contains a bunch of files, it will automatically create a new subfolder for you.

Enjoy!

Image source: bandisoft.com