OOC: We already have it that Hitler was a world leader. And that he was in Germany.
OoC/ Making him a painter, sculptor and architect doesn't mean he can't be a world leader too. /OoC
What you need is a powerful and, obviously, evil influence on Hitler early on in his life, I hear there was some sort of racist Nazo party [or something like that] in Germany at the same time Hitler was there. If he had attended one or two of their rallies it might have made him a Nazo.
With Hitler's charisma and winning personality on their side, the Nazo party wouldn't have fizzled out, as it did, its staunch opposition to the Hitler-led liberal [liberal for the time] government proving its downfall in OTL, with Hitler on their side, there may be no stopping them.
I think the real effects will be felt during the Second Great War, without Germany on Britain's side against Gaullist-Fascist France, we might be seeing a Grande L'État Français forming, with Britain suing for peace!
With France and a similarly-run Germany ruling most of Europe, a war with the USSR may be inevitable. Gaulist Fascism is directly opposed to Stalinist Communism, with only Poland between the two powers, they'd come to blows soon enough.
OoC/ Gaullism, ITTL, refers to De Gaulles' own branch of Fascism, De Gaulles being the leader of France ITTL, [obviously]. /OoC