Alex proved to be a strong and insightful leader for Power Pack, rallying them to win several important battles. However, he also occasionally exhibited an explosive temper; it was sometimes unleashed upon his siblings to disastrous results. Alex's outburst resulted in the entire team being located and kidnapped by the Snarks. When his youngest sister, Katie, was Energizer, he bullied her to such an extent that she compared him to the team's archenemy, Queen Maraud, and voluntarily gave up her powers to the Snarks.
The oldest Power sibling by several years, Alex often expressed a desire to cultivate friendships outside of the Pack. He had an on-and-off relationship with a girl in his class, Alison (sometimes spelled 'Allison') McCourt; this friendship would last throughout most of the series. Like his sister Julie, Alex also occasionally clashed with bullies at school. One of these, Johnny Rival, would prove to be a serious threat: he suspected Alex's powers, believed he was a mutant, and brought a gun to school to attempt to kill him.
Following an encounter with Hobgoblin and Spider-Man, Alex and Johnny buried their differences and became friends. This relationship was short-lived however: Johnny's older brother was a drug-addict and dealer who was killed by the police during a robbery to fuel his addiction. Alex had tried to prevent it and Johnny blamed his interference for his brother's death. This rejection prompted Alex to destroy a drug-house. Johnny was himself opposed to drugs; in one scene he is shown angrily ordering some boys away from a drug dealer who was goading them into buying heroin.
Afterwards, he returned their abilities back to them and promised not to take them again, but was later forced to reclaim them again to aid in the Warriors' battle against the Soldiers of Misfortune. Eventually, Alex explained to Julie and Jack his reasons for taking the Pack's powers into himself, which angered his siblings, especially Jack.
Among Alex's tenure with the Warriors was the encounters against Spidercide, a brief fight against Psionex (with then Night Thrasher and Rage on said team at the time), Protocol and the Soldiers of Misfortune, and both the Sphinx and Advent.
Alex's final mission with the Warriors was when they fought the Dire Wraith Queen Mother Volx (who had already stolen the Torpedo suit from Mickey Musashi, Power Pack's Smartship Friday, and Rom's Neo-neutralizer). The team succeeded in destroying her plans (along with the Dire Wraith as well), but at the cost of nearly destroying Friday.
Alex has been identified as one of the 142 registered superheroes who are a part of the 50-State Initiative.
After having his gravity powers forcibly removed by Jakal, Alex received the energy powers previously held by Katie. He renamed himself Destroyer, but found himself struggling with the moral issues his new power's lethal potential raised. Alex also pushed the upper limits of the energy power's capacity for absorption; in a battle with the Sentinel Master Mold, he disintegrated almost the entire bulk of the multi-story robot's body, causing his body to swell with stored energy. In the process, Alex found that exceeding his normal absorption limits generated intense pain, impaired his ability to think clearly, and made it difficult to release the stored energy. In a later adventure, he was also shown to be highly volatile in this state, prone to random releases of energy on physical impact.
After a third power switch, he received the density powers previously held by Jack and Julie and took on Jack's former identity as Mass Master. Alex was the first Power sibling to use the powers to turn himself into a liquid state and further developed the abilities so he could create a density blast of solidified air.
Alex underwent a transformation into an actual Kymellian, which started with mild hair loss. It was eventually revealed that Alex had learned of his parents kidnapping and had been kidnapped himself by Queen Maraud and a Kymellian Technocrat and was replaced by a clone which reverted to its original Kymellian form. The real Alex eventually escaped from captivity in Maraud's ship and rejoined his siblings.
Along with his siblings, Alex possessed Kymellian healing powers. Usually, he was required to work with his siblings to generate and use this ability; however, he occasionally accessed it on his own.
With his siblings, Alex owned a Kymellian smartship, Friday. The ship acted as an unofficial team advisor and accompanied the Pack on several missions.
Alex wore a costume of unstable molecules created by Friday. The costume existed in an extra-dimensional space known as "Elsewhere" and could be summoned with voice commands. The costume was later modified to include a mask.
During his first stint with his gravity powers, Alex also wore a set of wings which he designed himself after learning more about the effects of gravity and inertia in school. The wings, which were sewn by Julie and attached to his costume with straps, allowed him to propel himself and "fly" through clever manipulation of gravity and occasional use of air currents, instead of relying on Lightspeed to carry him. Alex passed the wings on when Jack acquired the gravity power, but they were destroyed during Power Pack's encounter with the Marauders during the Mutant Massacre.