Reformed, Returned and Really Trying

AU. With Albus dead, there's only one wizard left to continue his fight. His oldest friend. His true love. There's no better choice for defeating a Dark Lord bent on murdering all muggleborns than the one wizard who gathered them under his banner once before. True, things went a little out of hand, but Gellert Grindelwald has changed. If only everyone else would realise this...