Actually we can't use that Asajj Ventress lost also to Anakin as a weakness. Fact is she survived...
Asajj Ventress fell into a canyon after Anakin overpowered her during a lightsaber battle, which she survived, but just barely. She was sent to a planet where she was placed in a bacta tank by Count Dooku and given cybernetic modifications, which amplified her rage. When Kenobi was captured by Count Dooku, he was brought before the tank in which Ventress was contained, and was subsequently attacked by her, who detected him in her trance. She fought against both Kenobi and Anakin, only to be abandoned by Dooku, who ordered some of General Grevious's Magna Guards to kill her as she ran towards Dooku's shuttle. Enraged and wounded, Ventress tried to kill Kenobi who was trying to help her, only to be dealt a mortal wound by Anakin. Before she was put on a ship to Coruscant by Kenobi, as she lay dying, she told him the location of the the Separatists' next target and let go of her anger and rage. However, Ventress did not die, placing herself in a Sith Trance, and while on the shuttle, emerged from her trance, and ordered the pilots to take her as far away as possible from the war, Dooku, and the Jedi.
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