1> All time greatest achievement = farming and food creation.
2> 20th Century's greatest achievement = the latex condom
3> So far the greatest achievement of the 21st Century = The defeat of HR669 :-P
4> All time worst achievement = Religion.. all of them.
5> 20th Century's worst achievement = overfishing the oceans
6> So far the worst achievement of the 21st Century = The Patriot Act