'Supergirl' season 2 spoilers: two past baddies to ask Supergirl for a rematch

Supergirl (Melissa Benoist) will be having a rematch against two of her biggest villains when "Supergirl" returns to The CW for the second half of season 2.

TVLine revealed that Livewire (Brit Morgan) and Metallo (Frederick Schmidt) will be back to challenge Kara Danvers/Supergirl in the upcoming episodes of the series.

Livewire, whose real name is Leslie Willis, first appeared in a season 1 episode. She used to be one of Kara's colleague in CatCo who turned into a vengeful metahuman after being electrocuted by a lightning. She plotted to use her newfound powers to kill Cat Grant (Calista Flockhart), but Supergirl managed to defeat her and put her behind bars. However, Livewire managed to escape and team up with the Silver Banshee (Italia Ricci) to face Supergirl and The Flash (Grant Gustin) in a special crossover episode with "The Flash" in season 1.

Metallo, on the other hand, was introduced early in season 2. He used to be hired to kill Lena Luthor (Katie McGrath) but was turned into a cyborg by Project Cadmus after being severely injured when he attacked the CEO of L-Corp.

However, the events leading to the return of the villains are still under wraps.

Executive producer Ali Adler also mentioned that there will be other fan-favorite villains who will reappear in the future episodes of "Supergirl" season 2, but the list of the recurring characters are still concealed at the moment.

Aside from the past villains, Supergirl will also face a DC Comics popular baddie named Mr. Mxyzptlk when the series returns after the winter break.

Mr. Mxyzptlk is known as one of the greatest enemies of Superman, who happens to be Supergirl's popular cousin. But according to Comic Book, no actor has been cast for the character at the moment.

"Supergirl" will return to The CW on Monday, Jan. 23, 2017.