Zoom

"Zoom" is a mysterious and immensely powerful Speedster who's origins are currently unknown. He becomes known to Barry Allen and his team when it is revealed that it was he who promised to take "Atom-Smasher" home if the latter killed The Flash.

Biography
Zoom allegedly told "Atom-Smasher" about The Flash, telling the former that the latter was a hero, though not worthy. He sent him to kill The Flash, promising that he would take him home if he did so.

Zoom later had an encounter with Barry that caused him to miss the funeral of a person close to himself and Oliver Queen. In the NYCC Comic Con Sizzle Trailer for The Flash Season 2, Jay Garrick explains that whilst Barry reform the singularity, he was having a fight with Zoom in his world. And Jay Garrick also explains that Zoom's goal is to make sure he is the only speedster in any world in the multiverse.