Any kite line can be hazardous, but stunt lines are thinner, stronger, and move at high speeds close to the ground. If someone wanders into your flying range, land your kite immediately. Tell onlookers to stand behind you, the safest place to watch. Most people have no idea that a kite or its line could harm them. Don't fly your stunter in so much wind that you can't control it.
Some kites generate tremendous pull, even in moderate winds.
Never fly near overhead lines, in stormy weather or with wet lines. Many stunt kites have conductive graphite spars. Contact your utility company for assistance. It's best to assemble your kite once indoors before you take it out to fly. Also check it before each flight to be sure everything is set correctly.