Remove your Google AdWords account
Follow the instructions on the provided link to deactivate your account (you can later reactivate it if you like).
It is sadly impossible to remove your AdWords account. This is even more unfortunate because for the rest of your life, you will be responsible for any content on the web pages associated with your AdWords account (i.e. the ones for which you once advertised). This means, even if you sell your domain and someone else puts completely different content on it, YOU will remain responsible for that content complying with Google’s AdWords terms of service so please keep this in mind.
The best (‘least worst’) thing you should do is keep your AdWords-associated domains and not sell them. Any competitor or ill-minded person could put ‘illegal’ content on it, for which you will be held responsible. Probably you can’t do much about it and your Goodle AdWords account may become locked, until you resolve the problem.
Direct removal link: http://support.google.com/adwords/bin/answer.py?hl=en&answer=2424604&rd=1
Helpful Trick: Removing online data
Helpful Trick: Remove third-party logins
If you signed up for AdWords using a third-party login such as Facebook or Twitter, you probably want to revoke all access from AdWords. Click here to find out how.