Power off -> Hold Volume Up + Volume Down simultaneously while plugging the device into a PC via USB. Critical Precautions
Using a like Odin or Smart Switch is the ultimate "nuclear option" for fixing software issues. While it requires a bit of technical comfort, it is the most effective way to breathe new life into a malfunctioning Galaxy device. samsung download mode factory reset tool
The reset tool did not flash the userdata partition correctly. Solution: Re-enter Download Mode and use Odin with the PIT file (Partition Information Table). Check "Re-Partition" in Odin (dangerous – only for experts). Power off -> Hold Volume Up + Volume
Searching "Samsung download mode factory reset tool" online yields many shady results: The reset tool did not flash the userdata
Select using the volume keys and confirm with Power. Critical Considerations
You cannot factory reset purely from Download Mode without a firmware file. You must flash the "Home_CSC" file contained within the firmware.