To counter the shortest thread, I’ll start this one, limited to GB&I courses. Pointless everywhere else in the world where carts come before design... could say that the cart comes before the horse in fact.
In Ireland, the worst transition I can think of is a 500m trek between 9 green and 10 tee at Macreddin in Wicklow. Also about 300m from 18 green to the clubhouse. Plus the steepest dropshot Par-3 I know where you have to walk halfway back up the hill to the next tee. Painful.