Монстр (2014, Корея Южная)

Bok Soon, managing a street stall while caring for her sister, earns a reputation as the "psycho bitch" due to her uncontrollable rage. Her life takes a dark turn when serial killer Tae Soo murders her sister, fearing she discovered his secret. Fueled by vengeance, Bok Soon seeks to settle the score with Tae Soo, who is determined to eliminate her as the last threat. Their gripping battle spirals into an electrifying showdown, with the question of survival hanging in the balance: the fiery Bok Soon or the ruthless Tae Soo?

(Source: MyDramaList)