One of the biggest dangers posed by an unsafe e-bike is fire hazards. You should always choose a UL 2849-certified e-bike system and battery when purchasing an e-bike.
Riding an e-bike bike places loads of stress on the frame, fork, brakes, and wheels. You need higher quality components to ensure a smooth stable ride when riding at speed, and to help you be able to stop on a dime, in rain or shine.