Mine.
I'll pick the Titanic disaster, over 1500 people died for no reason. Had the Captain had a brain he would have steered the great ship back to the very monster iceberg that it hit and tore it's hull open, It may have took as little as 20 minutes to go back and connect with the iceberg and off load the passengers on the cold yet safe iceberg but Captain Smith decided to just do a slow sink that took 2h.40mins
65 years later in 1977 a Captain did the opposite and saved his crew and passengers, the MV William Carson sailing out of eastern Nova Scotia struck an iceberg in close to the very same waters, while the ship was smaller the 158 on board everyone were transported to the very iceberg that tore it hull open and everyone was rescued before it sunk in under 90 minutes