It depends on the situation. If they threaten you with a bad review, that’s the time to refund the order. If they say they hate your work, ask them why. You can also send a custom offer to make revisions, or use resolution center for the same purpose.
It’s important to humanize yourself in front of your buyer. Say “I did my best” or “I really worked hard on this” or “I don’t usually make revisions, but I’m making an exception for you.”
Suppose they message you before ordering, and they want to purchase your most expensive package which takes the longest, tell them “Since we don’t know each other, I think it would be better if you order my $10 package. I would rather refund $10 than $50.”
Also, be honest with them. If they want to order your trademark package and you only check for trademarks in the USA and they live in Mexico, tell them they’re better off ordering another package.
Another tip is to give referrals. You deliver an order after the buyer asked for a revision, the buyer has questions about your work. Tell him/her that seller x, y, and z also do what you do and they will be happy to help you. Doing this also encourages other sellers to refer you.