Outbreak Perfected is a fantastic pulse rifle that is a throwback to Outbreak Prime from Destiny 1. 

To obtain this weapon you have to complete a hidden (and challenging) quest:

1) Go to Titan.

2) Complete the Enemy of my Enemy world quest.  There are three steps to this quest.  You must do them all.

3) Enter the Bad Neighbours Adventure.

4) Play through until you come to an area with Hive.  You will see a Shrieker near a room glowing red.    

5) Go in the red room and open the vault door. 

6) Move through to the communications room and search for an Interact Option  It is on the right side of the room. 

7) You should now have a Fallen Transponder.

8) Head to the European Dead Zone.

9) You will need to enter the following Lost Sectors to find their transponder nodes (The Drain, Whispering Falls, Atrium and Widow's Walk)

10) Head to Nessus.

11) You will need to enter the following Lost Sectors to find their transponder nodes (The Carrion Pit and The Rift)

12) Zero Hour Quest - Visit the Farm

13) From the landing area go right and enter a basement. Talk to a Fallen Captain. Take the quest and you're off. 

14) Zero Hour consists of some basic mob fights and some annoying platforming.  Don't get frustrated. Keep at it...You've got this!  You may want to have some sort of shield breaking weapon in your loadout as you will encounter plenty of shielded enemies.  Other than that, it's a common sense follow the path type of engagement with one