Okay, Luna and Pitch are similar because both felt unappreciated, leading them to be evil, both represent nightmares (Nightmare Moon, Pitch can make nightmares) and both tried to destroy the elements that protect people of the world. (Elements of Harmony, the Guardians' elements)
o....nice
Oop, almost forgot. They also tried to persuade the rebellious member of the main characters into joining them. (Rainbow Dash and Jack Frost)
o wow
Thank you thank you. Hold your applause.
Haha lol..