"The more you struggle, the more energy drains from your body until you pass out or die."
Psycho Threads are thread-like magical barriers first used by Bujin, followed by Bido and Zangya. The user points his or her hand at his opponent and traps them with thin strings of purple energy, sealing their power. Struggling against the threads only exacerbates their effects.
This attack is first used by Bujin against Future Trunks in the movie Dragon Ball Z: Bojack Unbound. When Piccolo is easily dispatched by Bojack, Trunks transforms into his 2nd Grade Super Saiyan form and attacks Bojack with a barrage of blue energy spheres, which Bojack easily withstands. Future Trunks decides to attack Bojack head-on when Bujin traps him with the Psycho Thread, sucking the Super Saiyan energy out of Trunks. While the Saiyan is paralyzed, Bido throws a sharp piece of rock at Trunks, attempting to kill him, until Vegeta shields him, and proceeds to fight Bojack.
This attack is later used on Gohan while in his Full-Power Super Saiyan form, with the same effects as used on Future Trunks. He manages to break free mostly because of Mr. Satan being sent through, with Bojack shooting down his car. It is last seen against Super Saiyan 2 Gohan, though the young Saiyan easily dispatches the technique.