There’s no real good guys or bad guys, but I have to give the entente a bit of a stink eye for their peace just setting up another, even worse, war to come.
I think it’s kind of pointless to play the “who’s worse” game for wars that don’t involve a certain man with a little moustache or something on that level of psychotic evil simply due to how subjective it can be (and I prefer to at least try and be objective regardless of my own thoughts for the sake of professionalism), but if I had to make a choice, I would specifically look down on France for being overly harsh on Germany and the USA for its republicanism fetish setting up Eastern and Central Europe for a nightmare of dictatorships for the next 70 years instead of keeping the Habsburgs and Hohenzollerns around and empowering them to keep politicians in their rightful place (ie; far away from real power). I don’t really have anything against the other entente powers, they made some bad moves but I can chalk a lot of that up to “it’s war, what do you expect”
The Central Powers did some horrible things in the madness of war, and had they won outright, I don’t think things would be too much better than OTL, once Princip pulled the trigger, the 20th century was destined to be a shitshow from start to finish, but at least a Central Powers victory probably wouldn’t have led to Hitler.
I think everyone could have conducted themselves much more honorably, it was an all around awful war, but the circumstances of the time put the wrong people in the wrong positions and kept the right people out of them. This was an age dominated by ambitious, fiery, and nationalistic politicians with little to no regard for typical morality or even simple pragmatism, it was a perfect storm for atrocities of all kinds and no country’s hands weren’t stained by at some blood (except Albania and Montenegro I suppose)