So.... did anyone forget about WW2 which was far worse than WW1?
TOTAL tangent time, here.
WW2 was a much bigger, spread-out conflict than WW1, with ferocious fighting in general. But, purely pound-for-pound, I don't think anything matches the charnel-house slaughter, wanton destruction, traumatizing horror, and political fallout of WW1.
As the first truly mechanized war (The American War of the States being the first modern war), the pure butchery of the Great War was unprecedented in human history. An entire generation of young Europeans were predominantly wiped out. Historic locales were forever altered or destroyed. Regions were razed and covered with craters, barbed wire, and trenches. Cities were evacuated and demolished. Civilians were decimated and displaced only to starve later. And recovery was weak, as it instigated a world-wide depression that only the United States was isolated from, and then only for about ten years. WW2 was bad and larger-scale, but WW1 was a God-forsaken grindhouse. And had it not been for the intervention of the United States, delayed though it was, they might still be taking pot-shots out of trenches over there, as it, itself, was a culmination of over a hundred years worth of build-up.
Following the war, the Japanese who were part of the Allied powers were slighted by their non-inclusion at Versailles, which pissed them off enough to build themselves into an industrialized powet that couldn't be taken for granted the next go-around...ultimately setting them back decades until the 80's. The German Empire was dismantled and its people punished for something they had no powet to prevent, which engendered the rise of the likes of Hitler and led to it being a checkerboard piece throughout the cold war. It's only been within my lifetime that the reunited Germany has reasserted its position in European affairs. Russia was distracted by the war to bring the Red and White Bolsheviks together long enough to fight, but finally the Reds would stab the Whites in the back and institute Lenin's Soviet Union, the first and greatest bastion for communism, a wart on the ass of human civilization for a hundred years now that has resulted in more human suffering than any other system second to Islam.
Speaking of which, the colonial system which had basically concentrated powet in Europe, was utterly destroyed (except the British Empire, but it would never recover) leading to destabilization world-wide as the empires holding things together largely disintegrated. This was most notable in the dissection of the Ottoman Empire which gerrymandered the Middle-East into straight-line bordered nations that yugoslavia'ed warring groups together and brought about a multitude of internal conflicts, coup d'etats, and the reintroduction of terroristic Islam to the world.
I'm forgetting a lot of stuff, primarily because I haven't studied it in a long time, and it's past bedtime (gotta be back at work around daybreak), and it's not welcome in this thread. But I'm always amazed at how much WW1 directly affects life today and how it's often overlooked because of the horrific scale and cost of WW2. But war's hell, regardless.