How to unpair Redmi Watch 2 Lite?
1.Open Mi Fitness App and click More Settings > Unpair in the Profile Home page.
2. After the watch restores factory settings, it will be automatically unbound from your phone.
After unbinding, the watch will be restored to factory settings and all data will be cleared.
https://www.mi.com/global/support/faq/details/KA-07273/