It's The Good Advice...That You Just Didn't Take

Hitler on Gandhi, and Gandhi on Hitler:

Hitler advised the British to kill Gandhi. (Wikipedia claims that Viscount Halifax in 1937 'was also to listen politely to Hitler's advice on how he should have handled difficulties in India ("Shoot Gandhi!") and the meetings were generally uncomfortable.')

Gandhi, apparently, advised the Brits not to fight Hitler, except with non-violent resistance (apparently urging Britons to 'Let them take possession of your beautiful island with your many beautiful buildings. You will give all these, but neither your souls, nor your minds.')