How to reset login password of an instance?

Content

Is there a way to reset the login password for an instance? I have an instance where opc user had a password set. That password is no longer working. Is there a way to reset it ?

]$ ssh 10.0.3.4
Enter passphrase for key '/home/opc/.ssh/id_rsa':
Permission denied (publickey,gssapi-keyex,gssapi-with-mic).