I don't know about worst, but one at a well known course IMO is Walton Heath Old. It is a very long par 3, about 230 from the back to a green with a very busy road on the right which is OB, and someone's backyard left about 20 yards left. Very tough opening hole and listening to the cars whizzing by just makes one think, "don't go right".
It is the only hole on that side of the road and talks to move the clubhouse and the opening hole entirely to the other side have been discussed for a while. I think it is too demanding as a starter and a hole needed to be shoehorned to make 18. If/when the club can get the necessary permissions I think it will be an improvement.