If you are one of those freelancers out there who are using the services of Upwork, you may find it useful to check out your contract first before ending it. You may need to contest the feedback from your client if you find it necessary so that your feedback history will not be tainted with a two-star or one-star rating.
Just go to all your contracts and select the contract from your client. Click on the Terms & Settings part and from there you can see that you can request feedback changes. You can discuss it first with your client before requesting any feedback changes.