I would have said the "Machtergreifung", aka when Hitler got in power in 1933 over Poland 1939, since that's the point that started it all.
Suez Canal Crisis over Sputnik's launch?
Yeah, that one really doesn't fit
1900's I would have said "flight". 2000's had some of the worst natural disasters in history, would have put several of them above 9/11. e.g. the boxing day tsunami that killed approximately a quarter of a million people.
Definitely Flight for the 1900's. However, 9/11 had way more far-reaching consequences worldwide than the tsunami (or any other natural disaster) had. Not even Katrina could fit, as it just went back to the status quo afterwards and couldn't convince the US to stay in the Paris agreement.
The Nintendo eShop rating Thread: http://gamrconnect.vgchartz.com/thread.php?id=237454
The Steam/GOG key gifting thread: https://gamrconnect.vgchartz.com/thread/242024/the-steamgog-key-gifting-thread/1/