If you use a first-person zoom scope(ACOG,CQB...) when hiding in cover and using a shield, the enemy on the right cannot see you and only you can attack.
This is the video link
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With this, legendary missions can be cleared in 15 minutes in solo play, and it makes for an unpleasant experience in PVP.
Link to the 15-minute clear video of the legendary arena
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Anyone who doesn't use this glitch is stupid, is this intended for gameplay?