Continuity mistake: During the scene in which Alex attacks the two henchmen looking for him on the island, we see him attack the first guy and take him out. As he goes for the second bad guy we see that the bad guy has a pistol in a holster strapped to his waist. As Alex flips this guy over the pistol and holster disappear (most noticeable when the bad guy hits the ground). It is then back in place when Alex removed the gun to shoot a third bad guy coming toward him.
Revealing mistake: After Alex has crushed Zhang's hand in the cogs on top of the crane we see that while covered in blood there is no other damage to Zhang's hand. He even manages to move it and his fingers when in fact all the bones in his hand should have been crushed and the muscles and skin torn leaving his hand in tatters and unusable.