Liu Kang's spirit fighting his possessed corpse.
Spirits are noble species of the dead. Liu Kang became a spirit after being killed by Shang Tsung (with Quan Chi's help) and having his soul drained from his body.
After Raiden sacrificed himself to kill Onaga, the explosion eventually killed Shang Tsung. Liu Kang, along with the sorcerer's other victims, was freed from Shang Tsung's grasp.
Liu Kang decided to stay in Outworld instead of going to the afterlife to assist in the war against the Dragon King. He then discovered that his corpse was on a killing spree, killing his fellow Shaolin Monks in the Wu Shi Academy. It is at this time that Liu Kang allied with Ermac and became friends with him. He happily trained Shujinko in learning his techniques as he was aware that Shujinko was deceived by Onaga.
Liu Kang and Ermac succeeded in freeing his friends from Onaga's control but he was unsuccessful in controlling his body.