I agree on the importance of being sure the pedal tightens against the crank arm, not against the wrench but I've also never seen the need to gorilla-tighten pedals. I've always installed them "good and snug", guessing maybe 5 to 10 N-m, and that has always been plenty. The pedals never loosen and never damage the crank arm. Shimano specifies 35 - 50 N-m on some of their SPD pedals and that seems hugely excessive.