I saw my husband fight alongside Severus Snape, and I ran to join them against Kingsley. Kingsley tried to kill both my former teacher, and husband, but I put up my strongest shield charm and used a very rare killing curse that caused burning of the internal organs before death. It was not an official Unforgivable Curse, but from my research in the Restricted Section of Hogwart's library, I knew a lot of nasty hexes and curses that take a lot of skill to wield.