Stocking

Stocking is a gluttonous gothic angel and one of the main titular heroes of Panty and Stocking with Garterbelt... that is, until literally the last minute of the last episode when she reveals herself to be a demon and murders Panty, cutting her up into 666 pieces. She then leaves with Corset, who is resurrected as a blob from Brief's penis despite the latter being killed earlier. There is absolutely nothing whatsoever in the series even remotely foreshadowing this twist, which makes no sense even by this obscene show's standards. The creator studio, Gainax, is infamous for bizarre twist endings that infuriate fans, and this ending is by far the most extreme example of this ever, to the point that it qualifies as a parody of this tendency and was probably an outright act of trolling. Despite the ending card explicitly stating that the story will be continued in a second season, this alleged second season has not been announced and likely does not exist, the promise of it being yet another deliberate act of trolling the fans by giving them false hope.