Logged into 4 iPhones and 2 iPads - how can I remove my account or deactivate them all except one?
If you have the devices simply go to Settings>iCloud turn off Find my iPhone, and sign out of iCloud, then tap on Settings>General>Reset>Erase All Content and Settings.

If you don't have th devices the only options you have is remote wipe, or change all passwords for your accounts.  Remote wipe is an iCloud feature.  Go to www.icloud.com from a computer and sign-in. Click on 'Find my iPhone' tap on the device name and you will see an option to 'remote wipe'.  This can be done on your iPad with the Find my iPhone app.

If your devices are not found in Find my iPhone then change your iCloud/AppleID password(s) at myappleid.com.  Change all your account passwords.

Lastly, don't forget to deauthorize those devices from iTunes.  From a computer go to the iTunes Store click on 'Account' then click on 'Deauthorize All'.