Is Windows Defender enough for Windows 8.1 security?

[afternoon]

Hello,
I wonder is Windows Defender enough for Windows 8.1 security? I see that it can be easily bypassed from registry or powershell.

 

[Xyberbat]

The person in front of the computer is the weakest link. Defender is merely a very capable tool to assist in security.
When in doubt, I always double-scan downloaded files with a second anti-virus scanner.