You must first unroot via KingRoot, then flash the stock firmware using Odin (Samsung) or Fastboot (others).
After the process finishes, a "Root Successfully" message should appear. How to Verify Root Access kingroot android 601 install
If KingRoot fails or if you prefer a more transparent rooting methodology, the traditional system-less approach is recommended: You must first unroot via KingRoot, then flash
If KingRoot fails, modern rooting for Android 6.0.1 typically requires more manual "systemless" methods: You must first unroot via KingRoot
Your device may reboot automatically one or more times during the process; this is normal behavior for kernel-level exploits.
Often leads to "Root Failed" or soft-bricked devices. 🛠️ The Installation Experience