If Germany still had a Kaiser

[buritobr]

Let's consider the monarchy didn't end in November 1918. A parliamentary monarchy was established following the British model (remember: Friedrich Ebert supported keeping the monarchy). Wilhelm II resigned and a descendant became the Kaiser.
Two scenarios could have happened
1) The new Kaiser is committed to democracy, but since the monarchy still exists, the far-right become not so angry, Hitler doesn't become the chancellor and there is not another war in Europe
2) The new Kaiser dislikes the new regime, starts to work close to the NSDAP. He supports Hitler becoming the chancellor and the rest of the history is similar to the real life. Remember: Italy and Japan had monarchs, but their far-right dictators were not the monarchs. Something similar could have happened in Germany

[buritobr]

Hitler still becomes Chancellor (it's kind of hard to not appoint the leader of the largest party in the Reichstag to the Chancellor's position), and World War II starts slightly later, as Hitler presumably needs Kaiser Wilhelm (who presumably is still Germany's head of state) to die first in order to seize dictatorial powers.

I don't think it would be necessary. Italy had a king and Japan had an emperor when they entered in the war.