Волан-де-Морт
Known Ministers for Magic include Millicent Bagnold (before the books begin), Cornelius Fudge, Rufus Scrimgeour, Pius Thicknesse (under the Imperius Curse, controlled indirectly by Lord Voldemort), Kingsley Shacklebolt (at first temporarily, but later known to be permanent) and Hermione Granger.