Scott was a villain who fought against the X-Men. Just like in the mainstream timeline, Scott and his brother Alex were separated from their parents when their plane was attacked by a Shi'ar spaceship. This is where Age of Apocalypse deviated from the original canon. In this timeline, both brothers were picked up by Sinister, one of Apocalypse's Four Horsemen, and raised as his foster children. Unbeknownst to them, their father Christopher Summers was eventually found by Sinister and given over to the Dark Beast for medical experimentation.
Both Alpha mutants, and both holding the rank of Prelate, Scott and Alex Summers dominated the new mutant aristocracy in Apocalypse's America. Sinister employed the brothers to operate his breeding pens, acting as security, and sometimes performing as a special ops unit. Scott's ability to show emotional restraint in battle earned him Sinister's favor over Alex, fueling a dangerous rivalry between the brothers. This rivalry worsened when the brothers reunited with their real father - Christopher Summers - but were forced to fight him.
Sinister's preference for Scott over Alex also spilled over into his genetic experimentation, as with Scott's DNA Sinister planned to create a super-mutant strong enough to oppose Apocalypse. After capturing the X-Man Jean Grey, Sinister believed that he has found Scott's genetic match, and used their combined DNA to produce a child, Nate Grey.
Despite an initial belief in the doctrine of mutant superiority, Scott has reservations about the ethics surrounding his work, primarily in terms of excess. These concerns grew substantially once he met and became enthralled with Jean Grey, a prisoner and "race traitor". Though Scott planned to release her on his own time, Grey's husband, Weapon X, broke in and liberated her himself. Scott fought back against Weapon X, severing Weapon X's hand but losing an eye in the process. Jean escaped with Weapon X, who remained an enemy of Scott.
In the meantime, Scott increasingly found himself questioning the treatment of prisoners, and secretly started releasing them. This did not go unnoticed by his brother Alex, who still harbored hostility against him. Alex re-captured Jean in order to use her against Scott, successfully exposing his brother as a traitor. Although Jean had no love for either brother, she decided to trust Scott and they attempted to escape together. Along the way the two meet Nate Grey, their genetically engineered son, though they remained oblivious to the truth of their connection to him. Eventually, Alex tracked down Jean and Scott then killed them both. In retribution for Jean's death, Weapon X killed Alex.
Normal human male with intensive regular exercise.