Little has been shown of Hakkou's origin. However, it has been theorized that he could be from Earth 2 and/or a Fukushima mutation. Power Girl seemed convinced that Hakkou was a minion of Darkseid and it was also noted by Huntress that his fighting style was similar to that of the residents of Apokolips.
Hakkou was created by Paul Levitz to be the first antagonist of the New 52 Worlds' Finest featuring Power Girl and Huntress. George Perez was the first artist to draw him.
Major Story Arcs
When Hakkou attacks a lab owned by Karen Starr (Power Girl) in Japan, he destroys a device created by Mr. Terrific named the quantum tunneler - a device Power Girl and Huntress hoped would allow them to return to their universe. The two friends attack Hakkou and are able to drive him out of the building, after discovering that Power Girl is abnormally vulnerable to Hakkou's radiation. Hakkou flees to a power plant where he begins to consume nuclear waste, making him more and more powerful. In an attempt to defeat Hakkou, Huntress bursts a coolant pipe onto the villain but finds the water to be contaminated with radiation, making Hakkou even more powerful.
Again, Hakkou escapes into the city, now giant size due to the vast amount of radiation he has consumed. When he starts attacking civilians Power Girl manages to use a telephone tower as a baseball bat and sends him flying into the nearby Tokyo Bay. Here, Hakkou attacks the docked, US Military boats containing multiple nuclear missiles. After getting instructions from Huntress, Power Girl throws a nuclear warhead straight into Hakkou's mouth, finally defeating (and presumably killing) him by overloading him with the nuclear blast.
Powers and Abilities
Hakkou is able to emit vast amounts of radiation and heat. He can also "feed" on radiation to increase his size and power, however, absorbing too much energy will cause him to die and his radiation will dissipate - it is unknown whether this over-absorption has to occur over a short period of time or not to have this effect.