saying that Churchill is the chief villain of WWII is obviously very silly and a claim you would only make if you were being deliberately provocative to sell content (or a legit nazi of course).
it’s reasonable to say that Churchill was a villain, and that his villainy is often underrated, but one of the reasons for that is because he was facing a much greater villain!
while there is no shortage of competitors in the villain stakes, you can’t overlook the fact that Hitler started the war that he wanted, attacked the most countries, attempted the most genocides, and had the most villainous ideology, publicly avowed and clearly expressed.
while you could mount a valid argument that Japan was worse, I think it’s difficult to find one specific guy on the Japanese side that was as clearly responsible for the bulk of the atrocities as Hitler was for the Germans, and while there is a lot to say about Stalin since his career was much longer, Russia was fighting defense for much of WWII and his biggest crime was allying with Hitler at the start!
“Hitler was the villain of WWII and one of the biggest villains of the 20th century and perhaps human history” might be a tired cliche but only because it’s true; we should not forget that he was only one of so many other villains (many of whom he learned from!) but that doesn’t justify downplaying his villainy out of contrarian pique.