Then maybe we’re talking about an unbalanced combination of weapons and perks. From my point of view, that remains the only explanation. Maybe he needs to change his playstyle to counter yours.
For example, I played against a Predator with the nickname Samhain13youtube, who positioned himself very precisely and shot plasma from behind bushes, trees, etc. We could barely see him to shoot back. I managed to hold him off at the helicopter while my teammates escaped, so we won. I died but who cares.