!!! S P O I L E R A L E R T !!!
There are three endings once you make it to the end. For all three endings just do the following:
The Good of the Many: (Good) -
Once you are told to make a choice turn around and charge up the Singularity with LB.
One TMD to Rule Them All (Neutral) -
Kill Barisov and Demichev for this ending.
The Needs of the Few (Bad) -
Just kill Barisov for this ending.
Once you are done with an ending just go back to the main menu and click continue to do another ending.