Quicksilver (Last Avengers Story)

Quicksilver is normally an on-and-off villain in Marvel, varying from an antagonist to an anti-hero - much like his father, Magneto and his sister, the Scarlet Witch - this tradition extends to the alternate reality of the "Last Avengers Story" but due to the "grim-dark" nature of the story his flaws were much darker and violent, to the point he became a murderous madman.

In the "Last Avengers Story" reality Quicksilver seemed to harbor unnatural affections for his sister, so much that he began to hate her lover - Vision, this animosity grew to murderous levels as Scarlet Witch and Vision had children and on the day of their wedding Quicksilver attempted to kill Vision.

Racing at Vision with his superhuman speed Quicksilver intended to murder his rival, only for Scarlet Witch to step between them - attempting to use her Hex powers to stop her crazed brother she instead caused him to fly into her at superhuman speed, killing her instantly.

Quicksilver proceeded to run himself off a cliff to be with his deceased sisters, the senseless carnage was witnessed by Scarlet Witch's two children and Vision, upon seeing the distress on his children's faces and the murder of his wife-to-be, grew to gigantic size and shut himself off from the rest of the universe, presumably to grieve in his own way.