What was the worst year in history? I find it remarkable how many people give 21st century examples. I suspect this has more to do with us having better information on more recent tragedies. It also may be that we're more sensitive to more familiar environments. So the mongol conquests of the 13th century just doesn't seem as important as a world war of the 20th century.
The best answer:
Some 65.5 million years ago, the Chicxulub asteroid struck what would one day be Mexico’s Yucatán Peninsula. It ended up incinerating all life for hundreds to thousands of miles and causing a perhaps mile-high tsunami that wiped the East Coast of North America as clean as a billiard ball. And that was just the first day of a very bad year—it got worse.
