The Flash: Rebirth

Professor Zoom, master of the Negative Speed Force, has brought Barry Allen back to life in order to give himself the chance to tarnish the Flash's heroic legacy. But while Barry and all the other Flashes may outnumber him, Thawne has one big advantage. He claims that his Negative Speed Force allows him to change the past. In fact, he claims he's already done it by going back and murdering Barry's mother. And now, he's planning on killing Iris, just before Barry falls in love with her.