Teen Titans (2003)

S03E02 X

A new criminal has emerged in the city—Red X, Robin's old nemesis. Consumed by guilt, Robin believes he is responsible for this resurgence and is determined to prevent Red X from acquiring a potent chemical called synovium that could enhance his powers. Robin is relentless in his pursuit to capture this former dark side of himself, but he soon discovers that a more sinister scheme is lurking just beneath the surface.