Go to your Google Account at myaccount.google.com
Sign in if prompted
Open Security
Under Your devices, select Manage all devices
Review the list of devices
Select each device you want to sign out from
Click Sign out
Repeat for all devices
Change your Google Account password
Enable 2-Step Verification
Check Recent security activity for unknown access
Remove any unfamiliar recovery phone numbers or email addresses
Revoke access for suspicious third-party apps under Security > Third-party access
Sign out of Gmail, Chrome, and other Google services on devices you no longer use
If needed, use Find My Device or device settings to remove your Google account from a lost device