WWI was objectively the most world changing and sets the stage for the entire modern era, if you squint WWII was just the Extended Edition of WWI all that being said WWIII was still my favorite.
« Ce n'est pas une paix, c'est un armistice de vingt ans » — Ferdinand Foch about the signing of the Treaty of Versailles in 1919.
Often translated as "This isn't a peace treaty, it's an armistice for twenty years." but some might prefer "This is no peace, it's a twenty-year ceasefire."