Story:

Royal Dash: Do you really think you can rule Equestria like that ?!

Harmony: Oh stop it, you'll be cleared out now!

Royal Dash: And? You will not get far with your reign, you will not have strong magic to protect. You bits so hate fulfilled but that brings you nothing, you need love and friendship, only so can Equestria persist.

Harmony: Your stupid words do not help anyone!

Royal Dash: You'll see that Harmony! You will not be able to do anything, you only hate everything.
I may not have magic like you, but I have something you do not have, friends!
And friends are very important!
And through them I have a strong magic deep in my heart, the magic of friendship!

The door, locked by Harmony's magic, opened and Royal Dash's friends came in.

Harmony: What?! .... but .... but how is that possible?

Royal Dash, Magical Star, Sprinkle, Lucky Apple, Crystal Spark and Angellys began to float in the air.

Royal Dash: That's what I told you, friendship is stronger and now you'll see how strong friendship can be.

The eyes of the 6 began to light up white and a colorful trail formed and connected them all.
Everything around her stung with lights and Harmony was finally defeated by the magic of friendship.

Transformed into her normal form, Harmony now lay on the floor of the hall.

Harmony: Uhh ... what ?! HOW?! YOU!!!

Harmony looked wide-eyed at Royal Dash.

Harmony: It's all your fault !!! Had you not been my plan would worked!

Royal Dash: What do you want to do now ?! Harmony, you do not scare me anymore!
I now know how to defeat you and my friends will always help me, you will not be able to do anything !!

Harmony: We'll see that !!

Harmony targeted Royal Dash with her magic, but Harmony's magic vanished shortly before her.

Harmony: .... oh these are only consequences for a bit time!!!

Celestia came to Harmony.

Celestia: Harmony, I am very disappointed in you!

Harmony: Mom! Uh ... it's all her fault!

Celestia: No, she is not to blame, only you alone and now go!

Harmony: .... okay ....

Harmony left the hall.

Celestia: Thanks a lot Royal Dash, you saved us all!

Royal Dash: Me? Oh, my friends helped me!

Magical Star: No, the princess is right

Celestia: In the end, it was all up to you to beat the Harmony and you could defeat her through your experiences of friendship.
I'm very surprised how well you are familiar with friendship!

Royal Dash: Friendship is easy to understand!

Celestia: Not for everyone! I know ponies who did not know each other as well as you did with friendship, and also with studies!

Royal Dash: I have good friends, I owe that to them. We also have to go now.

They went to Ponyville in Twilight's Castle.