Which WordPress security tool will help me fully protect it?

The WordPress security is crowded by a mix of firewall (app based or SaaS), scanning and monitoring tools or plugins, hacking cleanup tools or services, automated updates tools, backup tools, and of course professionals. All claiming to keep your web property secure. Short answer, none.  Why? Because each one of them will provide a granular security component. It will help lock one aspect of your web properties security, but not all of them at once. When you go for one option, you will have a false sense of security until you get hacked at some point. Additionally to that, not all the popular options out there is the best on what they do ;)