Hitler would keep a career in the army (he say a lot loved his time in the army...
He'd be useless in a peacetime army which would be greatly reduced from wartime levels. He might wangle a job in the German occupation government of Belgium or Poland or wherever
Mussolini Depend about italy but he comes from a victorious one so...50/50 depend a lot of other residual butterflies.
He'd have an even better chance of taking over, as Italy would be even more disgruntled.
Stalin ditto what happen in russia, maybe not come, maybe death if the white wins, wagging guerilla against white,etc.
Continues his radical career until killed by whatever puppet government Germany installs in Russia.
Chamberlain: He would have a good career as not munich-appaseament policies but depend how britain weather a 'defeat' or 'negotiated victory' conservatives will take a while comeback
As in OTL, enters Parliament after the war, is in government at various times. May become PM eventually.
Churchill: blame about gallipolli and if conservatives are punished along liberals his career would be over, maybe focus in literature
Churchill was a Liberal during WW I; he did not "re-rat" until 1923. The Liberals came out of the war as the party of victory, and then collapsed five years later. If the war is lost, they go down in flames at once. Churchill probably leaves. Whether he can get back into the Conservatives is another question.
FDR: depend about USA and his health, i can imagine two term at most ITTL.
If the U.S. stays out, then he never becomes Asst Sec of Navy, and isn't nominated for VP in 1920. But the entire course of U.S. politics is so drastically altered that his career can't be forecast.
Might be killed in the war.
If he survives, he may become an advocate of military reform. However, it is also likely that victorious Germany forces France to reduce its army. OTOH, he had staff and teaching positions, and might be part of the retained cadre. In defeated France, his radical ideas might get a lot better reception.
Petain: ...the French Hindenburg...
Only if he doesn't lose the key battles.
Chiang Kai-Shek: depend what happen post war china and if germany support nationalist even more that otl. Possible the leader an unify china
A China-Germany alliance is quite possible. A CP victory prevents a USSR, which therefore will not be competing for influence in China.
Pretty much, unless a major Pacific war breaks out before say 1935.
Radical anti-Austrian activist. Or emigrant to the U.S.