The Stronger the Opponent, the Stronger I Get, but My Strength Is Unknown

After Bu Yunlu transmigrates to the cultivation world, the System forcibly binds her to a single technique. With that technique, she becomes invincible under heaven. Onlooker 1: "I saw it with my own eyes. Three months ago, she beat a late-stage Golden Core demonic cultivator until he coughed up blood!" Onlooker 2: "That's nothing. Last month, she went toe-to-toe with an elder of our sect at the Deity Transformation stage and didn't lose an inch." Onlooker 3: "I heard she smashed the Demon Venerable's palace a few days ago, then walked away without a scratch. Her cultivation must be unfathomably deep." Onlooker 4: "Lu Yu, the number-one cultivator in the cultivation world, personally admitted he couldn't beat her. Doesn't that make her the best under heaven?" The head of Xuanyin Sect: "Huh? Is this Bu Yunlu you're talking about our outer sect disciple Bu Yunlu, who's only at the Qi Refining stage?" The onlookers: "Qi Refining? An outer sect disciple??" Bu Yunlu: "You might not believe me, but I only know one move. With it, I'm invincible under heaven!" Everyone: "What move?" Bu Yunlu: "It's called 'Fifty-Fifty.' I can't beat anyone, and no one can beat me. I always end up evenly matched with my opponent." Everyone: ????? Lu Yu: "Excuse me, are there any requirements for learning this technique?" Bu Yunlu: ????? Reader advisory: The setting is wildly imaginative, so don't take it too seriously. Enjoy the story. Theme: The Middle Way.