You will have to take advantage of an application that can manage browser's add-ons. For this procedure, download AdwCleaner and scan your PC. At the end of the scan process, switch to the browser you're using and make sure the 20-20 add-on remains checked. Press Clean and the add-on will be removed. Reboot the PC, then start the software again and initiate a new scanning, just to be sure.
The software offers the possibility to remove the add-on from all browsers.