In Metro Exodus, you will encounter a sect worshiping a giant mutant catfish. Let's figure out how to kill it and get the Fisherman achievement.
The catfish (Tsar-Fish) can be found in the «Volga» location. Believe it or not, there is actually a way to kill this clumsy monster. Unfortunately, you will have to wait until the end of the level to do so. Here is what you need to do to kill the Catfish.
The Catfish cannot be killed until you head to the train car to retrieve it. Go through this entire area until you reach the giant red door. On one side, there is a ladder and a gray door leading to a side area. Go there.
Now you need to create a trap for the Catfish. All the objects you can interact with are on the right when you go down the stairs. Use the bell first.
Now wait for the Catfish to approach. Quickly cut the rope to drop the body.
Pull the lever on the right to drop the debris on the Catfish.
All that's left is to watch the cutscene of the Catfish's death and receive the trophy.