As a Buddhist monk, Thommanon was a great teacher and yogi, but saw the worst of the mass killings in Cambodia from US military attacks that unleashed the further slaughter and madness of Pol Pot. This drove him insane, turning his beliefs away from the compassion of Buddha to what he saw as the destructive power of Shiva.
Wonder Man accompanied his love interest, Alex, to an LA suburb where Cambodian refugees lived to do research for her refugee movie proposal. They went to a Cambodian Buddhist church to see Father Phimeanakas. There they encountered Brother Thommanon in a maddened state. Enraged and speaking of seeking vengeance for the slaughter of Cambodians, he revealed visions of mass deaths and destruction familiar to the two Cambodians and Wonder Man (featuring the Supreme Intelligence in the wake of the Nega-Bomb's detonation on Hala.) These were manifested by candle flames; however this mental blast unwittingly siphoned ionic power from Wonder Man and was fueled by the hero's fear and anger. Thommanon collapsed to the floor and Phimeanakas took him to a healer. Later, Lotus sent three armed hoods to question why the monks talked to Wonder Man, but they were incinerated by Thommanon, who had just transformed into Angkor. He crushed one of the hoods' guns with his hand.
Angkor smashed his way into a busy shopping mall in L.A.'s Pico District, tearing it apart, randomly killing the terrified people, seeking to turn the parking and shopping fields into the killing fields he had endured in his native country, dedicating his kills to Shiva. Elsewhere, Spider alerted Wonder Man to Angkor's rampage and the ionic hero launched himself to stop him. The two fought in another destroyed mall, Angkor recognizing similar ionic power in his foe to his own. The two continued to fight but were fairly evenly matched with Angkor fueled by his rage.
Meanwhile, Lotus was contemplating just who Angkor actually was and sought an angle that would benefit her nefarious plans.
Back at the mall, Angkor was able to grab Wonder Man and forced him to see a vision of the pain and destruction wrought on Cambodia. Wonder Man suddenly realized that Angkor was the monk he had met earlier. The guilt that he now felt, partly as a past munitions worker, weakened Wonder Man's powers, with the Avenger recognizing that Angkor was really in pain and not in full control of his actions. However, Angkor capitalized on this weakness and pounded into Wonder Man until the hero fell unconscious. Angkor then stomped off to continue his bloody quest for vengeance. Soon after, slowly recovering, Wonder Man sought the Avengers' help but they were too busy with the Infinity War.
Wonder Man's powers returned at a heightened level and he was determined to pursue Angkor. He made his way to the Avengers West Coast compound to seek their help directly, but they declined. The Living Lightning reported that he'd been monitoring the radio and that Angkor had not been sighted for the past hour. Frustrated, Wonder Man returned to the Buddhist church in an effort to try to understand more about Thom but found the charred bones of Lotus' hoods. Phimeanakas told the hero of Thom's pain and rage, but Wonder Man instead sought to match Angkor's rage with his own.
Elsewhere, Angkor made his way to a factory of National Ballistics that had manufactured the bombs and napalm used to destroy Cambodia. The killer sought to detonate the lethal chemicals still kept there in an effort to destroy Southern California to match the devastation he had witnessed and smashed his way inside. Wonder Man quickly caught up to the Cambodian and the two resumed their fighting. Just as Angkor tried to once more disorient Wonder Man by showing him images of destruction, but Wonder Man fought back, his rage making him stronger yet also fueling Angkor's power so that he was surrounded in golden flames. Phimeanakas watched from a distance as Wonder man kept brutally pounding away at Angkor, almost overpowering him until Angkor surrounded him with flame and images of death that he felt guilt over. Wonder Man focused again on his own anger and kept smashing at Angkor until he exploded, thereby killing the Cambodian.