Accelerator

Accelerator is Academy City's highest-ranked Level 5 esper in A Certain Magical Index. He begins as a ruthless participant in the Level 6 Shift experiment before becoming an antihero who protects people caught in the city's hidden conflicts.

Accelerator's path from antagonist to protector

Initially arrogant and emotionally detached, he is changed by the suffering of the Misaka Sisters and by his decision to save Last Order. His central motivation becomes atonement, even though he continues to present himself as a villain.

Vector control and his bond with Last Order

His Vector Change ability lets him redirect motion, heat, electricity, and other vectors, making him exceptionally difficult to harm. Brain damage later forces him to rely on a calculation device, while Last Order becomes the relationship that most clearly anchors his humanity.