I hope that's a joke.
.
1> All time greatest achievement: Way back! Using tools!
2> 20th Century's greatest achievement: Landing on the Moon
3> So far the greatest achievement of 21st Century: Stem Cell Research Progress.
4> All time worst achievement: Religion
5> 20th Century's worst achievement: Probably the Holocaust
6> So far the worst achievement of 21st Century: The astonishing number of people against the Homosexual Civil Rights Movement