Based on the provided information, Aggregor is the main villain featured in the first season of Ben 10 Ultimate Alien.
Aggregor: The Primary Threat in Season One
According to the Wikipedia entry for Ben 10: Ultimate Alien, the initial major conflict of the series revolves around a powerful antagonist named Aggregor. He is an Osmosian, a species known for its ability to absorb energy and matter.
Aggregor's primary objective at the start of the series is to amass incredible power.
Here's a breakdown of his actions and goals as described in the reference:
- Species: Osmosian
- Initial Goal: To steal the powers of five powerful aliens from the Andromeda Galaxy.
- Method: He kidnaps these five specific aliens.
- Escalation: Despite Ben and his team's efforts to stop him, Aggregor succeeds in his plan.
- Result: He absorbs the five Andromeda aliens into himself, gaining their combined abilities and becoming "virtually unstoppable."
This absorption makes him a significant threat, driving the narrative for a major portion of the first season as Ben and his team must find a way to counter his new, amplified power level.
Aggregor's transformation from a kidnapper to an overwhelmingly powerful entity by absorbing others makes him a central and formidable foe early in the series' run.
