There have been accidents where one pilot gets confused, panics, inappropriately pulls or pushes the control column, and the other pilot does not manage to get control from them and the aircraft either stalls or nosedives into the ground. Recent example is Atlas flight 3591, but there have been other airliner accidents, and Dan Gryder mentions it as probable cause of some training flight accidents.
Now in aircraft with mechanical controls, when opposing forces are applied to the control columns (including on the Atlas B767), they usually split and each half controls the respective aileron and half of elevator, which is rarely enough to recover. On the other hand on fly-by-wire Airbus, the non-confused pilot can simply press the control priority button and recover (the confused pilot is unlikely to press the button the necessary way to win a priority contest).
But a B777 has connected fly-by-wire control columns. Is there an emergency option to disconnect them and specify which one the aircraft should respond to?