Centauraus, you have a point, but did not answer the OP's question...
Here are the top three which I've seen handled really badly:
Engine failure with loss of thrust on final approach/in landing configuration (requires swift action to maintain control: flap 15, bug plus 15, accurate flying);
Engine fuel control failure on takeoff (EG only)(requires swift action to control flight path and respect limits, and action of the engine surge/limit/stall checklist from memory - it's not a recall list);
Engine failure in idle descent (EG only)(usually mis-diagnosed as gen failure).
Not a failure, but the most frequently screwed up maneouvre (both in the sim and on the line) is the two-engine go-around.