Plenty of ways. The human throat and temples are disproportionately fragile for their importance, and a sharp blow to either could easily cause a mortal wound we don't have the equipment to treat. The carotid artery is very close to the skin, and so are major arteries in the arms and legs. Internal bleeding from a poorly placed contusion might not even be noticed until it's too late. And that's not even counting the possibility of impacts with surrounding objects, or someone else having a power that could escalate the situation.