Answer: President Woodrow Wilson attended the peace talks of 1919 at Versailles in France with the expectation that his grand plan for worldwide social justice, contained in his "Fourteen Points", would be readily accepted by the other leaders of the victorious powers, Britain, France, Italy, Japan et al. Instead he encountered their fervent desire to exact revenge on Germany for having begun the war (which it actually hadn't) and by making them accept that responsibility extract reparations from them.
Due to ill health (Wilson may already have been experiencing micro-strokes which affected his judgement) he eventually abandoned his grand peace plan and agreed with the much harsher peace terms imposed on Germany, which inevitably led to the rise of the National Socialist party (the Nazi's) and World War Two, which was faught to undo the terms of 1919.
In that sense his contribution to world peace was an abject failure, resulting in circumstances that would eventually plunge the world into another even more devastating war two decades later.
Step-by-step explanation: