Unauthorized phone showing in Device Manager - how can I remove it?

[AC Question]

Last week my phone (or maybe it was my google account) was compromised.
Settings on phone (background color, clock time) were changed.
Installed Android device manager and it shows another phone added to my account in mid-October.
How can i get rid of this guys phone?
Does it mean he still has access to my phone? Already changed password to another strong one.

Thanks! in advance

 

[B. Diddy]

Welcome to Android Central! Is the added phone completely different from any of the ones you've had? Does it specify which model of phone it is?

If you changed your password, that should be all you need to do. If you want to be extra safe, turn on 2-factor authentication.