It took three years for IF and Compa to gather the tiny amount of Sharicite - peoples' belief in the CP Us, given form - used to free Nepgear at the start of the game
The Conquest ending! Nepgear is forced to kill the CP Us and their sisters, including her own sister. Because they knew that they cannot defeat Arfoire without the Gehaburn. The Candidates express their desire to join their fallen sisters in death. Vert opts to take the sword and with it, Neptune's and Nepgear's lives so that she can live for Chika, and she is murdered anyway by Underling, forcing Vert to ask Nepgear to use the sword to finish the job so that she can at least help stop Arfoire. The kicker? The victory was Pyrrhic, serving not to save Gameindustri from destruction, but making its demise inevitable.
One of the Chirper endings becomes this in hindsight. When you talk to Blanc in Lowee after saving her, she decides Nepgear's changed for the better, and she'd like to be her friend. If you happen to be on the road to the Conquest Ending by this time, Nepgear will wind up killing Blanc later, the woman who just stated her desire to talk with Nepgear more and have a long friendship with her. Enjoy that.
Blanc: Fine. I'll try to talk to you more. We'll have a long-term friendship.