The Apocalypse Add-on for Stellaris has 10 achievements.
Own 4 active Gateways
Use a World Cracker to destroy another Empire's capital planet
Defeat a Fallen Empire's Titan fleet with a Titan of your own
Own a Citadel with 40k fleet power
Unlock all 42 Traditions
Explore a Natural Wormhole
Destroy another Empire's Colossus while it is in the process of firing on a planet
Own 200 Starbases (Outposts are counted)
Use a Global Pacifier to shield a planet belonging to Fanatic Purifiers, Ravenous Swarms, or Determined Exterminators
Kill the Great Khan in battle