To stop Brave requesting to save new passwords to the Password Manager:
1) Go to brave://password-manager/settings
2) Turn off “Offer to save passwords”.
To delete passwords already stored in the Brave Password Manager:
1) Go to brave://settings/clearBrowserData
2) Select the “Advanced” tab.
3) Set “Time range” to “All time”.
4) Untick any boxes that are already ticked.
5) Tick only the “Passwords and other sign-in data” box.
6) Click the “Clear Data” button. Be warned, this will not just delete passwords on the local device, this will delete all passwords from all devices that are synced with Brave Sync.
7) Go back and remove the tick from the “Passwords and other sign-in data” box, so that you don’t accidently delete all your passwords (across all devices) in the future if you decide to start using the Brave Password Manager again.