Xadhoom! is the third and last "trial" issue of PKNA. It was written by Alessandro Sisti and Ezio Sisto, and penciled by Stefano Intini under the pen name "Paul Ackerman".
As stated by the title, it features the first full appearance of recurring character Xadhoom (although she briefly appeared in issue 0.
An Evronian ship is hidden in the asteroid belt. There, General Zotnam is angry that a planet like Earth has resisted them, and orders to take measures against the obstacle known as the Duck Avenger. Of the three ships sent, two are hit for what seemed a humanoid.
At Ducklair Tower, Donald is helping with the moving of the new tenants, the Channel 00 News division. Despite being tired after that, Uno sends him to check a swarm of unusual objects flying around the city. They turn out to be explorer drones programmed to find the Duck Avenger, but when they ambush him, they are suddenly attacked by a powerful woman. After the Evronians escape, she turns her attack against the Duck Avenger and wrecks the 313-X.
Back at Ducklair Tower, Uno shows to Donald a new vehicle for his masked crusade, but forbids him to use Ducklair's old cars in his civilian identity or he's draw too much attention. That night, Uno takes control of a satellite for observation at wide spectrum, so he can find the mysterious woman, who is in the Park. The Duck Avenger goes there and wants to talk, but the woman, who introduces herself as Xadhoom, attacks the Avenger again until the Evronians find him again thanks to another drone. After seeing the Duck Avenger fight against the Evronians, Xadhoom accepts to be his ally.
Donald offers Xadhoom his hospitality at Ducklair Tower, and when he finds she doesn't eat but instead "feeds" of thermonuclear processes, he gives her baking soda so it doesn't burn so much.
Donald goes back home to see Huey, Dewey, and Louie, but Huey tells that they must go to Africa with the Junior Woodchucks. A drone finds Donald, but as he isn't in disguise, it stops following him. However, Uno traces the drone and finds the Evronians are hiding in the Power Plant, which Donald confirms when he finds the security guard has been turned into a Coolflame.
That night, the Duck Avenger and Xadhoom sneak into the Power Plant, but the Evronians find them and trap them inside a force field, where they leave them to eventually suffocate. Since they are going to die anyways, the Duck Avenger asks Xadhoom what is her story. Xadhoom was Xado, a prominent scientist of planet Xerba who believed the Evronians came in peace and ordered not to take any measures against them. She was away working on an experiment to control matter and energy, and she returned to find Xerba devastated by the Evronians, so she swore to wipe the Evronians. When the Duck Avenger finds the bubble is powered by Duckburg's electricity, he asks Uno to turn the power off and they get free.
The Duck Avenger and Xadhoom face the Evronians, and Xadhoom explains her battle name means "creditor" in Xerbian, as she has a huge debt to collect because the Evronians owe her her world. After traqshing the place, Xadhoom leaves to search the Evronians' outpost in the solar system and tells that if she had used her powers to the fullest, she would lost control and become a nova.
Back at Ducklair Tower, the Duck Avenger needs Uno's encyclopedic knowledge to know what is a nova. When Uno explains it's the state of an exploding star and the consequences it would have, the Avenger faints.
Huey, Dewey, and Louie's trip to Africa is a reference to the Italian multi-part Junior Woodchucks story "Threat From Outer Space".