Deathloop is a game that is all about learning your enemies, their habits and gear, and using your knowledge as a weapon. The best way to do this is by focusing. Focusing on enemies gives you valuable information that you can use in later loops.
What makes focusing so important is that enemies will not be in the same location on different loops. These constantly changing scenarios will require you to be prepared for any situation and this is where focus comes in.
Focusing will do several things for you. It will reveal an enemy's loadout which is essential when facing those who have unique weapons. It can also warn you of unique behaviors and movements an enemy may have. Focusing can also reveal if an enemy is carrying on a trinket or not as well. Once you have focused on an enemy, you can even track their location on the map.
Consistently using focus is an excellent way to stay ahead of your enemies and ensure you have more knowledge than them. If enemies know you are in the area, focusing will reveal this information and you will know that you need to play more stealthy to avoid gunfights.
For more information on Deathloop, check out What is the code to the safe in Colt’s apartment in Updaam in Deathloop? and What do you do with the Crank-Wheel in The Complex in Deathloop? on Pro Game Guides.