Microsoft Defender won't stop

[wincentID]

After the last patch Duhfender kicks off on boot, making boot time about 7 minutes since it conflicts with an existing commercial AV/firewall. I can't kill the proc in services. I tried taskkill in a shell as admin but it failed there too. I wouldn't object to it but as I said it's conflicting with an existing paid AV that I've been using for many years. I tried to start a program 10 minutes ago that usually takes <1 min to start, it's still not open. At this point I'm tired of arbitrary changes. My main system is UNIX-based, due to increasing issues w. Windows since 2005. I still need a system running Winblows for when I'm gaming but now I can't even do that. Is there a regedit I can do to prevent it from starting even if there's no other AV/firewall? As I said, I wouldn't be running the OS except there are games I play, one in which I have 4k+ hours, over the last 14 years, so I still need it, at least if I can get this done.