SmallBill:

If you have a twin with the left engine only running, the offset thrust tends to pull the plane to the right and the torque tries to roll the plane to the left. The two forces are opposing, making the airplane easier to fly than on the right engine only, where the two forces add. Provided both engines are conventional rotation.

Since this airplane is easier to fly with the left engine only, the left engine is referred to as the "Critical" engine. Losing the left is more a crisis than losing the right.

With counter rotating engines it doesn't matter which engine fails, the torque and thrust are subtractive for both engines.

The P-38 is a special case. With the right engine reversed there were bad turbulence problems, so it had the left engine reversed. Yes, this made the plane equally hard to handle with either engine out, but techniques were developed using this to increase the maneuverability of the plane; playing with the throttles gave it yaw capabilities that astounded the Jap fliers just before they died.

Bill.