The Federations Add-on for Stellaris has 10 achievements.
Have all eight ethics represented within your Federation
Build a Juggernaut
Construct a complete Mega-Shipyard
Be the leader of a max level Federation
Have a Diplomatic Weight of over 9000
Level up your Federation
Be a founding member of the Galactic Community
Refuse to belong to any club that would have you as a member
Humiliate an Empire that is in the Supremacy Diplomatic Stance, forcing them out of it
Denounce an Empire that is not actually in breach of galactic law while all major sanctions have been passed