Warning! The following story contains spoilers for the end of Good Omens Season 1.
The seeds for a follow-up season of Good Omens seemed to have been planted in the epic finale. In the sixth episode, now streaming on Amazon Prime Video, the angel Aziraphale (Michael Sheen) and his demon BFF Crowley (David Tennant) successfully thwarted the end of the world, but their final conversation hinted at an even bigger apocalypse to come: the inevitable war between angels and demons fighting against humanity. It was an ominous note to end on after a cheerful first season (despite the whole season centering on the impending apocalypse), and one that seemed to hold promise for an even bigger second season. If angels vs. demons were as epic as the first season of Good Omens showed, just think of how world-shattering it would be to see both sides team up against all of humanity. Now that’s an Armageddon!
Source: IGN.com Why Neil Gaiman Doesn't Want Good Omens Season 2