My most recent playthrough was of an exceptionally - aggressively, you might even say - friendly empire who's main goal is to achieve galactic peace & prosperity through making friends and having an exceptionally happy populace that is united under these ideals.
Making friends? Liberate and Vassalize - followed by integration once the puppet government has done its work converting them to my ethics. Also uplifting. (Especially if they are earth roaches, though they didnt spawn this round.)
Exceptionally happy populace? (Mandatory) bread and circuses for everyone!
United under those ideals? On top of the bread and circuses making everyone exceedingly happy, the bread genetically engineers everyone into conformists, and the circuses have mind control laser light shows.
There WAS that one big unfriendly empire of nasty slavers next to me that got eaten up by the unbidden before I could save them though. (Read as: I penned them in with the unbidden i summoned by stealing psi jumpdrives from a FE and they got eaten, before I swooped in and removed the unbidden, grabbing up all their territory)
In less than a couple centuries a galaxy of 1000 stars was one big happy family (including allies and loyal vassals)