255px-Fiona Fox
Fiona Fox is the main antagonist of Transformers: The Final Battle. Originally Fiona Fox was one of the many victims of Dr Ivo Robotnik's rise to power and was imprisoned as a child as a result of being abandoned by Sonic and Mighty.

Fiona, understandably, developed a grudge against the two for what happened and over time Fiona's grudge worsened the darker aspects of her personality until she eventually fell from grace entirely and became an outright villain.