It's generally not easy to remove applications on MAC. I perform the uninstallation in two different ways,1. Right click on the application(MAMP.app) and then show package content. Now you will be able to see the 'Contents' folder. Just delete that and clear your bin.2. Use the AppCleaner application for mac - http://www.freemacsoft.net/appcleaner/

If you used the the Bitnami MAMP installer from bitnami.com, you just need to go to /Applications/mamstack-version and there double-click the uninstall icon. It will automatically uninstall the full stack, removing the running processes.

I think it is not safe to use option one explained by @vinod, it could leave processes running in your system. Option 2 should work also if you installed the MAMP stack from the MAC Store.

By default, the uninstaller should be located in this directory:Applications folder → MAMP PRO → MAMP PRO Uninstaller.appHowever, if you can't find it, you can uninstall it with App Cleaner & Uninstaller. I've used this way and it has uninstalled the app completely without leaving any traces.