Villainous Saint: From the Start, I Won Over the Protagonist's Own Little Sister

[Villain power fantasy + master and disciple + ignoring fate + overwhelming background + crushing all opposition + decisive and ruthless + Immortal-Controlling Seal] After waking up, Qin Tian transmigrates into a fantasy world. He has exceptional talent, a fearsome background, and an immortal’s beauty. He thought his background would let him live a carefree life, but then his System awakens and he discovers that he’s a villain! The protagonist, whose cultivation he once crippled and whose meridians he severed, made a powerful return not long ago. Not only has his cultivation recovered, it has advanced even further, and he now wears a ring on his hand. Even his younger sister is the reincarnation of a Nine Heavens Sword Immortal. Before long, she’ll awaken the wisdom of her past life and cleave open the heavenly gate with a single sword strike. Faced with a disastrous start, Qin Tian is saved by his System and obtains the heaven-defying cultivation art, Immortal-Controlling Seal. From immortals to ordinary mortals, anyone branded with the Immortal-Controlling Seal, no matter their cultivation, has every action and even their life and death placed under Qin Tian’s control. A Nine Heavens Sword Immortal? A terrifying powerhouse reincarnated? They’re nothing but... The beautiful woman inside the ring, a terrifying powerhouse from the Upper Realm? She’s nothing but... When the protagonist’s master resists, Qin Tian simply brands her with the Immortal-Controlling Seal and forcefully subdues her... His junior sister’s master catches him teaching her to cultivate? Qin Tian simply brands her with the Immortal-Controlling Seal and teaches her to cultivate together with them...