You can automatically end a Campaign when a recipient replies. And, you can choose to have that mark the Campaign as a 'success' for that recipient.
To set this up, after you have created your campaign simply check the Unsubscribe boxes in the Settings portion of the Campaigns tab:
Both of these options will end the campaign and your recipient will not receive any more emails from you. And, you must have reply tracking for this to work.
Additionally - you can remove someone or a few people directly from the people section of your Campaign:
Lastly, you can remove someone from a Campaign in their group in the People tab of ToutApp.com: