Police helicopter crashes onto Glasgow pub
Twins are inevitably more complex than singles and that in itself can be regarded as making them inherently more dangerous- only because there is a greater chance of a systems failure or pilot error. For this reason more attention is applied by designers to mitigate the risks and to ensure that the advantage of two engines is not outweighed by the disadvantages. In a single you have no choice if your motor goes, a twin will stay airborne to get you back to base or extend the choice of Landing site beyond a simple cone. If both donkeys go, then you are no worse off than flying a single.
Single engine overflight of built up areas is prohibited for this reason which is why commercial, police, air ambulance all use twins. They don't have a choice- correct? Complexity is addressed by training and type conversion and in itself it isn't a threat.