If Nu Zu really can’t be put back in the bottle, why are our heroes still fighting the Colonel’s faction? They have a motivation to team up and kill Nu Zu before humanity is wiped out. Sui Ren is pretty safe. Well maybe there’s a conflict of interest between killing him now and killing him after Asylum is destroyed.
That said, it’s also not very easy for them to imagine killing Nu Zu. Plot-wise, it’s probably gonna be a mystical ass-pull thanks to Sergiu’s ability to read the texts, and maybe Sui Ren’s meme powers too. Else we get an End of Eva ending, which would be kinda funny but it wouldn’t really sit right.