There has been viruses that completely disable your Windows Defender by using registry, I couldn't find anything that could restore my Windows Defender so I checked out what it did and basically made a reverse for it.
*Save as batch file*
*Do not forget to run as admin*
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender\Real-Time Protection" /v "DisableRealtimeMonitoring" /f
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender\SpyNet" /v "SpynetReporting" /f
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender\SpyNet" /v "SubmitSamplesConsent" /f
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender" /v "DisableAntiVirus" /f
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender\Real-Time Protection" /v "DisableBehaviorMonitoring" /f
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender\Real-Time Protection" /v "DisableIOAVProtection" /f
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender\Real-Time Protection" /v "DisableOnAccessProtection" /f
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender\Real-Time Protection" /v "DisableRealtimeMonitoring" /f
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender\Real-Time Protection" /v "DisableScanOnRealtimeEnable" /f
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender\Reporting" /v "DisableEnhancedNotifications" /f
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender" /v "DisableAntiSpyware" /f
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender\MpEngine" /v "MpEnablePus" /f
reg add "HKLM\System\CurrentControlSet\Services\WdBoot" /v "Start" /t REG_DWORD /d "4" /f
reg add "HKLM\System\CurrentControlSet\Services\WdFilter" /v "Start" /t REG_DWORD /d "0" /f
reg add "HKLM\System\CurrentControlSet\Services\WdNisDrv" /v "Start" /t REG_DWORD /d "0" /f
reg add "HKLM\System\CurrentControlSet\Services\WdNisSvc" /v "Start" /t REG_DWORD /d "0" /f
reg add "HKLM\System\CurrentControlSet\Services\WinDefend" /v "Start" /t REG_DWORD /d "0" /f
reg add "HKLM\Software\Policies\Microsoft\Windows Defender\MpEngine" /v "MpEnablePus" /t REG_DWORD /d "1" /f
reg add "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run" /v "SecurityHealth" /t REG_SZ /d "%windir%\system32\SecurityHealthSystray.exe" /f
reg add "HKLM\Software\Microsoft\Windows\CurrentVersion\Explorer\StartupApproved\Run" /v "SecurityHealth" /t REG_BINARY /d "060000000000000000000000" /f
reg add "HKLM\Software\Microsoft\Windows\CurrentVersion\Run" /v "SecurityHealth" /t REG_EXPAND_SZ /d "%%%windir%\system32\SecurityHealthSystray.exe%" /f
reg add "HKLM\System\CurrentControlSet\Control\WMI\Autologger\DefenderAuditLogger" /v "Start" /t REG_DWORD /d "1" /f
reg add "HKLM\System\CurrentControlSet\Control\WMI\Autologger\DefenderApiLogger" /v "Start" /t REG_DWORD /d "1" /f
reg add "HKLM\Software\Policies\Microsoft\Windows Defender\MpEngine" /v "MpEnablePus" /t REG_DWORD /d "1" /f
reg add "HKEY_CLASSES_ROOT\Drive\shellex\ContextMenuHandlers\EPP" /v "(Default)" /t REG_SZ /d "{09A47860-11B0-4DA5-AFA5-26D86198A780}" /f
schtasks /Change /TN "Microsoft\Windows\ExploitGuard\ExploitGuard MDM policy Refresh" /Enable
schtasks /Change /TN "Microsoft\Windows\Windows Defender\Windows Defender Cache Maintenance" /Enable
schtasks /Change /TN "Microsoft\Windows\Windows Defender\Windows Defender Cleanup" /Enable
schtasks /Change /TN "Microsoft\Windows\Windows Defender\Windows Defender Scheduled Scan" /Enable
schtasks /Change /TN "Microsoft\Windows\Windows Defender\Windows Defender Verification" /Enable
If there is anything that doesn't work please let me know.
Programs that Uninstall Windows Defender (that I know about):
ItroublveTSC (stub, not the actual builder)
AlienCrypter (stub, not the actual crypter)
Bitrat (stub, not the actual builder)
VenomRAT (stub, not the actual builder)
WSHrat (stub, not the actual builder)
Let me know if there are any more.

PLS LIKE
*Save as batch file*
*Do not forget to run as admin*
Hidden Content
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender\Real-Time Protection" /v "DisableRealtimeMonitoring" /f
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender\SpyNet" /v "SpynetReporting" /f
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender\SpyNet" /v "SubmitSamplesConsent" /f
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender" /v "DisableAntiVirus" /f
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender\Real-Time Protection" /v "DisableBehaviorMonitoring" /f
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender\Real-Time Protection" /v "DisableIOAVProtection" /f
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender\Real-Time Protection" /v "DisableOnAccessProtection" /f
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender\Real-Time Protection" /v "DisableRealtimeMonitoring" /f
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender\Real-Time Protection" /v "DisableScanOnRealtimeEnable" /f
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender\Reporting" /v "DisableEnhancedNotifications" /f
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender" /v "DisableAntiSpyware" /f
reg delete "HKLM\Software\Policies\Microsoft\Windows Defender\MpEngine" /v "MpEnablePus" /f
reg add "HKLM\System\CurrentControlSet\Services\WdBoot" /v "Start" /t REG_DWORD /d "4" /f
reg add "HKLM\System\CurrentControlSet\Services\WdFilter" /v "Start" /t REG_DWORD /d "0" /f
reg add "HKLM\System\CurrentControlSet\Services\WdNisDrv" /v "Start" /t REG_DWORD /d "0" /f
reg add "HKLM\System\CurrentControlSet\Services\WdNisSvc" /v "Start" /t REG_DWORD /d "0" /f
reg add "HKLM\System\CurrentControlSet\Services\WinDefend" /v "Start" /t REG_DWORD /d "0" /f
reg add "HKLM\Software\Policies\Microsoft\Windows Defender\MpEngine" /v "MpEnablePus" /t REG_DWORD /d "1" /f
reg add "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run" /v "SecurityHealth" /t REG_SZ /d "%windir%\system32\SecurityHealthSystray.exe" /f
reg add "HKLM\Software\Microsoft\Windows\CurrentVersion\Explorer\StartupApproved\Run" /v "SecurityHealth" /t REG_BINARY /d "060000000000000000000000" /f
reg add "HKLM\Software\Microsoft\Windows\CurrentVersion\Run" /v "SecurityHealth" /t REG_EXPAND_SZ /d "%%%windir%\system32\SecurityHealthSystray.exe%" /f
reg add "HKLM\System\CurrentControlSet\Control\WMI\Autologger\DefenderAuditLogger" /v "Start" /t REG_DWORD /d "1" /f
reg add "HKLM\System\CurrentControlSet\Control\WMI\Autologger\DefenderApiLogger" /v "Start" /t REG_DWORD /d "1" /f
reg add "HKLM\Software\Policies\Microsoft\Windows Defender\MpEngine" /v "MpEnablePus" /t REG_DWORD /d "1" /f
reg add "HKEY_CLASSES_ROOT\Drive\shellex\ContextMenuHandlers\EPP" /v "(Default)" /t REG_SZ /d "{09A47860-11B0-4DA5-AFA5-26D86198A780}" /f
schtasks /Change /TN "Microsoft\Windows\ExploitGuard\ExploitGuard MDM policy Refresh" /Enable
schtasks /Change /TN "Microsoft\Windows\Windows Defender\Windows Defender Cache Maintenance" /Enable
schtasks /Change /TN "Microsoft\Windows\Windows Defender\Windows Defender Cleanup" /Enable
schtasks /Change /TN "Microsoft\Windows\Windows Defender\Windows Defender Scheduled Scan" /Enable
schtasks /Change /TN "Microsoft\Windows\Windows Defender\Windows Defender Verification" /Enable
If there is anything that doesn't work please let me know.
Programs that Uninstall Windows Defender (that I know about):
ItroublveTSC (stub, not the actual builder)
AlienCrypter (stub, not the actual crypter)
Bitrat (stub, not the actual builder)
VenomRAT (stub, not the actual builder)
WSHrat (stub, not the actual builder)
Let me know if there are any more.

PLS LIKE