Continuing on the theme of WWII, I want to take a different stance and promote something, or rather someone, who is rather underrated and indeed has come to symbolise the failures which lead to the war.
Neville Chamberlain.
A name often associated with one action at one place, the treaty of Munich, but Chamberlain did so much more than that. In fact, he presided over the steady armament and preparation of Britain for an outbreak of war in Europe. Churchill came in as PM when it had all been completed, and carried in Britain in the defence and then offensive, but Chamberlain was the PM who laid the groundwork.
It's just a pity that all he is remembered for is a mistake in his foreign policy, but there's a lot of Presidents and Prime Minister who have history like that.