* Power: Queen Aleena is the rightful ruler of Mobius, and controlling her would give Robotnik ultimate control over the planet. He could use her authority to enforce his rule and exploit Mobius's resources.
* Revenge: In some stories, Robotnik blames Aleena for his downfall or for preventing his earlier conquest of Mobius. This fuels his desire to capture her and make her pay for her supposed betrayal.
It's worth noting that in some versions, Robotnik's specific goals shift throughout the story. He might initially want to capture her to gain power, but then his motives become more personal, fueled by a desire for revenge or a twisted ambition to rule alongside her.
Ultimately, Robotnik's desire for Queen Aleena stems from his insatiable greed for power and his unwavering ambition to dominate Mobius. He views her as a tool to achieve his goals, and her capture is a crucial step in his plan to achieve total control.