The Bhopal disaster is considered one of the worst, if not the worst, industrial accidents ever. It killed more than 2,000 people, and some death estimates run into the 15,000 range. It was absolutely horrific.
I first learned of the Bhopal disaster when Mike Ciresi was campaigning for the U.S. Senate. He was one of the lawyers representing India against Union Carbide, so I had to look up the case.