Certainly a four engine jet with an engine layout like a B747/A340 has two critical engines due to aerodynamic reasons. The outer engines are critical. If there is any crosswind then the upwind outboard engine is the most critical. With a twin jet the upwind engine is critical for the same reason in a crosswind. Other considerations are systems, i.e. hydraulics, electrics and pneumatics. An engine failure with one particular engine “could” be more critical than the other.