Just as a reminder: a prop does not always produce assymmetric thrust as may be implied in previous posts! Indeed the downgoing blade has a greater (local) AOA than the upgoing one and therefore produces more 'lift', but only if the aircraft is at a positive AOA. If the aircraft is flying straight and level there's no such thing as assymmetric thrust from a prop disc.
Obviously if you're going to lose an engine on any twin prop, the critical phase for this would be just after take-off, and the climb angle will then indeed produce the assymmetric thrust case, and yes you will have a 'critical engine' which indeed is the one with the downgoing blade closest to the fuselage.