So far there are no incidents that have been “the worst”, however we have had many accidents that could have ended much more badly than they did.
Take for example the following incident of a man in New York flying a drone off his balcony. He flew it beyond his line of sight, instead relying on streaming video from the camera to pilot his drone. When the video connection cut out, the drone crashed into a skyscraper multiple times, before tumbling onto the sidewalk below. Luckily, nobody on the sidewalk was hurt, but a 10lb drone tumbling from 50 stories towards the ground with its rotors spinning could cause serious injury if it had hit someone or fallen into a crowd.
The same can be said about this incident at a sports match. Luckily it hit an area of the stands where there was not too many people, however it could have ended much worse.
Drones are still only starting to become popular, so we are likely to see many more crashes as time goes on, and the future crashes may not be as forgiving as these up until now have been.
BONUS: Here is a look at some drone crashes involving animals. Surprisingly the animals seem to be the ones to walk away unharmed as the drone is destroyed from being knocked out of the sky in most cases.