This may seem like an odd topic, but hear me out.
Do you crouch in Halo 5 multiplayer? Arena or Warzone? If you do, you probably get more kills that if you did not.
When in a one on one battle, crouching can make all the difference. It is all about the hit box.
Halo 5 has a slight aim assist, even if you have it turned off. But when an enemy crouches, this hit box is moved suddenly, giving total control of where your gun is pointing to the player, subsequently missing shots. This makes the gun lock on and off in the space of a few frames.
Next time you are in a one on one battle, try crouching up and down whilst shooting them, you will find that more often than not, they will miss a few shots, and this could give you the advantage.
Tip: Don’t jump and crouch, this only would make you an easier target, stay on the ground and crouch. You can also boost when crouched.