Was WWII avoidable after the first world war? Had the Germans won would the second world war have been inevitable? or did the allied victory directly cause the catastrophic conflict that would follow?

Most, if not all, of your question require speculation which is not something we allow here. Any sort of 'what if' questions are reserved for /r/HistoryWhatIf. :) You are free to use our search function to find previous threads on the Versailles Treaty - I feel like that's where you'll find your answer to the question if WWII was inevitable after WWI.