Complex sentence: Takion's main nemesis was Stayne, his dark counterpart who was a nameless human woman transformed by Darkseid's power, and sent to keep Takion from achieving his true potential, and from discovering Darkseid's plan to destroy the Source Wall.
Split into simpler sentences: Takion's main nemesis is Stayne, his dark counterpart who was a nameless human woman transformed by Darkseid's power. She is sent to keep Takion from achieving his true potential and to prevent him from learning about Darkseid's plan to destroy the Source Wall.