While I hate the Schufa with a passion, it is not as clear-cut and automated as you make it seem. Before anyone can do shit with your Schufa score (or the other smaller credit reporting agencies arvato infoscore and Creditreform), they have to formally remind you of the debt that you have due to the charge-back before, and you can always contest fraudulent entries at the credit reporting agencies.

Additionally, you can and should file a police report for fraud when hit with such a scheme, it makes dealing with your card-issuing bank and the CRAs so much easier.