How to delete data from previous user on used watch

Do a factory reset of the watch. Always do that before you add a watch to your account to prevent that from happening.

To clean up already synced data is hard and some data can't be removed. There is a script somewhere in the forum for removing data for a specific device. I haven't used it and don't know if it is still being maintained.

e7andy  Is correct. Also make sure that this is posted on the thread for the specific watch you purchased since it has to do with the device and not the Connect account.