To unlock the exotic Nemesis Sniper Rifle in Division 2 you have to be in World Tier 5. You have to complete Tidal Basin at least one time, once you are done with all missions, Play Tidal Basin once again and follow the steps to find a Black Tusk Keycard, along with all different components of Nemesis Rifle. There are four components of Nemesis Sniper, first is found by dismantling a rifle while the other three can be collected only by killing three bosses.
How to Unlock Exotic Nemesis Sniper
Nemesis Sniper First Part – The Scope Location (The Tally)
While playing Tidal Basin for the second time you will come across an objective to destroy a Turret in the stronghold region. After destroying it a door will open up on your right, go inside on the top floor on the bunk bed to get a Black Tusk Keycard, that will be required to unlock the door that has Adrestia SR1 Rifle. Continue playing till you reach the hovercraft. Inside the control room look on the left corner from the entrance and you will find a backdoor. Use the keycard to access it and inside the crate you will find Adrestia SR1. Dismantling this weapon will give you the first part of Nemesis Sniper, that is a Scope – The Tally. The component will give you the clue for the next three components, if you check the description it will tell you about three bosses Klutz, Shorty, and Prime.
Nemesis Sniper First Part – The Barrel Location (The Scourge)
Go to Capitol Building stronghold, play the invasion mission. Kill the last boss “Prime” he will drop the second part Marksmen Rifle: Barrel – The Scourge. Complete the mission to progress to the next two steps.
For the next two two-parts have to play invaded missions at Roosevelt Island where you will might face Shorty and District Union Arena where you will face Klutz. Each of them will drop a exotic component. The exotic rifle is time based game and you have to wait two more weeks to get the other two parts.