Louis Mountbatten, 1st Earl Mountbatten of Burma (1900-1979).
Last Viceroy and first Governor-General of India, wherein he oversaw Partition and was certainly partly responsible for the supposedly 'unavoidable' deaths of at least 200,000 civvies because he had an irrational desire to finish ahead of schedule.
First Sea Lord; uncle of the Duke of Edinburgh and egotist and self-publicist extraordinaire.
Mountbatten had a number of ships sunk under him in the early part of WW2, including HMS Kelly - an episode which was made into a film by Mountbatten's friend (and possibly his homosexual lover) Noel Coward in In Which We Serve. Thus he managed to parley what would have been a career-ending failure for most of his naval contemporaries into public acclaim. Dashing, good looking and snobbish to the 'nth' degree, Mountbatten was promoted by Winston Churchill to head Combined Operations after the resignation of the Admiral of the Fleet Sir Geoffrey Keyes. The job - which gave him a seat on the chiefs of staff committee - was well beyond Mountbatten's abilities at this time. It's highly likely that, apart from his well known weakness for Eurotrash aristocrats, Churchill saw Mountbatten as someone he could easily control and manipulate. As chief of Combined Operations, Mountbatten was responsible for overseeing the planning that led to the farcical Dieppe Raid, although he subsequently tried to shift the blame to everyone from Montgomery to the doorman at the Savoy Grill.
Memorably described - by Field Marshal Lord Templer - as being "so crooked that if he swallowed a nail he'd shit a corkscrew."