Chaos Space Marines

Chaos Space Marines are the absolute worst antag that can appear on the outpost barring a Warp Storm. Heavily armed and armored and lacking in the sanity department, Chaos Space Marines are the replacement for the standard Nuke Ops.

Choice of Warband
Your actions differ depending on your Warband/Legion/the warband/Legion your bunch originally comes from. The ones currently available are:

World Eaters
The default, murder-happy Khornate Berzerkers, screaming about THE BLOOD GAWD and how good he is. You usually end up murdering every living soul.

Word Bearers
The deeply religious of the pair. Word Bearers are more likely to sacrifice and taunt their foes than outright slaughtering them like the Khornates.

-Also, make it a personal objective to become as much of a book as possible.(If you are not draped in layer papers you aren't living up to the wordbearer esque name.)

Red Corsairs
Alternatively, you can tell the Chaos Gods to piss off, and play with the Red Corsairs, badass motherfuckin' space marine pirates. Generally the most sane of the bunch, being Renegade Space Marines instead of Chaos Marines.

Your Single, Solitary Job that is 99.99999% Failproof
Get. Dat. Fukken. Disk.

It's easy as that. Get disk. Arm nuke. Leave.

Occasionally, you'll be given fitting Admin objectives, like KILL ALL THE FUCKERS AND PUT THEM IN A BIG BLOODY PILE FOR KHORNE or DEFACE THE STATION AND BRING IT UNDER THE FOLD OF KAYOSS. Do these.

CSMs usually get along with all antags (Word Bearers) or every antag except Slaaneshi Heretics/Cultists or Tzeentchians(World Eaters). Be wary.