According to reason, once a soul mark is imprinted, it is eternally impossible to eradicate. This has nothing to do with one's cultivation.
Even if the soul mark left by Ding Huan was from when his cultivation was weak, Lao Liu couldn't possibly remove it so easily.
Lao Liu believed it was removed because he cultivated the Little Universe Technique and had reconstructed his meridians and acupoints.
Then, after this guy partially recovered his memory, he used his own abilities in conjunction with the Little Universe Technique to remove the soul mark that Ding Huan left in his soul.
Of course, this removal was only what Lao Liu thought had happened.
In truth, after Ding Huan cultivated the Great Universe Technique, the soul mark left in Lao Liu's divine soul hadn't been removed at all. Instead, it had merged into the depths of Lao Liu's soul, becoming one with Lao Liu's spirit.
Unless Ding Huan took action himself, Lao Liu would never be able to remove that mark.
