This is how Nightmare Moon vs. Twilight and Twilight gives in to the dark side goes in
Nightmare Moon: Now I will destroy you, Sparkle. As I destroyed your Magic of Friendship.
[Twilight jumps to avoid the attack]
Twilight Sparkle: Nooo!
[She dodges another attack]
[Nightmare Moon prepares to finish Twilight when her friends show up. Nightmare Moon uses her magic to hold them in place]
Nightmare Moon: You are strong, Twilight, but only your hatred will give you the power to save your friends. Give in to the dark side.
[Twilight gives in to the dark side and fires red lightning at Nightmare Moon, who uses her magic to make a shield to block it. Nightmare Moon fires the red lightning back at Twilight, causing her to fall. Nightmare Moon then uses her magic to teleport Twilight's friends away. Nightmare Moon approaches Twilight]
Nightmare Moon: Ha ha ha. Very good...my apprentice.
[Twilight looks at Nightmare Moon as her eyes turn nebula blue]