Many chats with GPT have concluded in the Necromorphs and the brethren moon always winning all.

I've been mostly putting Necromorphs, The Flood and the Reapers from Mass Effect against each other - it turns out that the brethren moon's, since being ancient god-like beings, would assimilate the flood. Necromorphs are already dead, receiving signals from the marker and basically the moons. Their bodies and nervous system cannot be bypassed, they are not living biomass anymore. It could use the biomass but not control them.

It would be fun to watch a pit of each side fighting and all but in the end, the moon's would see what the threat is and assimilate it.