Hi,
a simple start for that discussion is,
with propellers, as long as they 're rotating the same way, a critical engine is determined simply because the yaw momentum is different considering the right or left engine...in case of failure of the "critical" one..
In other words the critical one is asking you more aerodynamic force to counteract yaw momentum...
For a jet engines, no critical engine , in that way of thinking exist...but other aspects have to be taken into account..
To answer your question, the critical engine will already consume all the aerodynamic power you get..so adding a crosswind...and you could be out of control..(directionnaly speaking)..
rgds