1. Germany was not made part of the post WW-I negotiations.
2. Full responsibility and onus to pay reparation of war were imposed.
3. Limits were imposed on its militarization in French bordering Rhineland.
4. Coal and Iron ore rich Alsace-Lorraine was given to France, and eastern districts to Poland etc.

Paris Peace conference and Establishment of League of Nations:

1. League  of  Nations  whose  mission  was  to  keep  peace,  lost  faith  of  many  countries  through  its inception  as  it  was  an  organization  to  only  perpetuate  the  power  of  victors  of  World  War  I (mainly Britain and France).
2. Germany was not even allowed to be part of it till 1926.

But there were factors other than these treaties which also contributed to the culmination of the Second World War:

1. Rise of the Nazi and Fascist Propaganda

1.       Promises of restoration of Germany’s position as world power, colonial  expansion  and  revenge from the perpetrators of treaty of Versailles by Hitler

2.       Organisation of armed gangs in Italy by the Fascists.

1. Appeasement of Fascist forces by U.S., U.K., and France to counter Soviet Russia

1.       As  per  Treaty of  Versailles,  German  army  was  limited  to  1,00,000 men  but  they  overlooked  the increase of its strength to 8,00,000.

2.       Indifference to Nazi and Fascist intervention to overthrow republicans in Spain and occupation of Austria by Germany.

1. Rise of Japanese imperialism

1.        Government of Japan passed in to the hands of the Shoguns or the military elites.

1. Formation of alliances

1.       Formation  of  Axis  power  of  Germany,  Italy  and  Japan  and Allied  Forces- Britain,  France,  Soviet Union, U.S. and China.

1. Failure of League of Nations to ensure peace.