Looking back over the last century or so, I was more than a little amazed to find myself forming the opinion that there is in fact one man responsible for the train wreck that lasted from 1914 til the present.
That man was Gavrilo Princip, the Serbian who - with the help of his scabby little co-conspirators - killed Archduke Ferdinand over some stupid nationalist nonsense, and started the non-stop arms races and bloodbaths that have characterized the years since.
I realize, of course, that the political situation was a powder keg just waiting for a spark...But so was the cold war, and as I look around, there don't seem to be many radioactive craters. Therefore, it is possible to squeak through these "powder keg" eras without the "inevitable" spark. In a thousand alternate realities, World War I probably would have happened anyway, had Princip's mother thrown him down the well as an infant, but this wasn't by any means certain.
Therefore, I'm putting the blame on him and his pals.
Can you even imagine what the world would have been like with no WWI? Without WWI, there wouldn't have been a WWII, and Hitler would have starved to death in an obscure artist's garret. The Russian revolution probably would have failed, almost certainly the Chinese revolution as well. The Ottoman Empire would still exist, so the Middle East wouldn't be so nutty. Nukes would have taken decades more to develop, as would space travel...though the motives for the space race would have been different, and maybe we'd have actually accomplished something. The entire national psychology of the USA and the UK would be vastly different, in a positive way.
So, here's to you, Gavrilo, you psychotic little fucking runt. You ruined the future. Way to go.
Or Kill Me.