Agility is mainly used to evade bullets and/or fleeing from a fight, but can also be used to eliminate an opponent more efficiently by using different strategies like the Run and Gun strategy.
Agility is extremely useful in huge maps allowing you to traverse them easily and much faster than any other player boosting other attributes. This can be extremely useful when taking down opponents, taking them out before they can react, or dodging that deadly single-shot bullet.
That being said, if you fail to dodge, you can take much more damage than if you wore Health -increasing armor, meaning you are able to be easily wiped out with a shot from a weapon like the Shotgun. As such, you might want to train yourself in dodging the mad fire of bullets Respawnables has on a day-to-day basis before applying them to multiplayer.
Agility is one of the deadliest attributes one could ever possess, especially when carrying single-shot weapons with great agility.