As Nuklon, Albert was a charter member of Infinity, Inc. and subsequently served in the Justice League. He took the Atom Smasher identity shortly before the founding of the current Justice Society of America, of which he was a charter member. He views Pratt's son, Damage, as a brother, and acted as an older brother figure to Stargirl. While Stargirl has (or at least had) some romantic feelings for Atom Smasher, he has not yet openly reciprocated.
For years, Atom Smasher cherished his role in upholding Pratt's legacy and constantly sought to prove himself worthy to his Golden Age idols -- especially when many of them became his teammates in the JSA. But when Albert's mother was murdered in a plane crash engineered by Kobra, he became consumed by vengeance. Not long after the fatal crash, Albert -- with the aid of Metron of the New Gods -- went back in time and replaced his mother with a weakened Extant, saving her life but murdering the supervillain.
When Captain Marvel's longtime adversary Black Adam reformed and joined the JSA, he and Rothstein developed a kinship; indeed, Black Adam once commented that he thought of Atom Smasher as the brother he never had. Encouraged by Adam, Atom Smasher grew frustrated with the JSA's moral boundaries, especially when Kobra blackmailed authorities into granting his release. Albert and Adam promptly quit the JSA after Kobra's escape.
Shortly thereafter, the unlikely duo settled each other's personal scores. Adam killed Kobra; Rothstein killed the dictatorial president of Kahndaq, Adam's home country. Atom Smasher helped lead a team of rogue metahumans (including former Infinity Inc. teammates Brain Wave and Northwind) that invaded the country and overthrew its oppressive regime. Atom Smasher initially fought against his JSA teammates in Kahndaq before deciding instead to help forge an uneasy truce -- Black Adam and his compatriots could remain in power so long as they never left the country.
Atom Smasher remained in the Middle Eastern nation for a time, although he eventually began to question Adam's motives. Rothstein perished while fighting against the Spectre, but was revived by Black Adam's lightning, and carried back to JSA headquarters.
He was later put on trial for his actions in Kahndaq and pleaded guilty to all charges. Whilst in jail, he was approached by the founder of the Suicide Squad, Amanda Waller (also White Queen of Checkmate). Waller recruited Al as part of a new group of covert operatives using the name, the Suicide Squad. Aware of Al's history with Black Adam, she sent the squad to San Francisco to sanction him. There, the Squad fought not only Black Adam, but Black Marvel Family members, Isis, Osiris and Sobek as well. Despite his prodigious strength, Al lost the fight against his old colleague. Recently, Al worked with the JSA to track the recently repowered Black Adam, eventually encountering him in a diner. The two notably did not fight, showing that their relationship is a bit more amicable.
Atomic Dispersal: As a result of exposure to uncontrolled Thorium radiation, the Atom Smasher's mass has become unstable. Al can grow, allowing him to grow up to 28 feet tall. At this height, Al is resistant to hits by all attacks from normal sized characters. With Atomic Dispersal, Al increases the distance between his own atoms, thus increasing his overall size. Under normal circumstances his mass would remain the same no matter how large he becomes. However, his mass increase power counteracts these effects, to a point.
Increasing his size beyond his optimal limitations causes Al great physical discomfort.