Coming from Rainbow "I made the impossible possible" Dash, that statement is meaningless. Every single one of the mane 6 except possibly Rarity and Applejack have some impossible power or two.
Rainbow Dash has the Sonic Rainboom, is fast and strong enough to compete with Applejack on the ground , and is effectively indestructible (Sonic Rainboom into a barn? Totally okay!).
Fluttershy has the stare. That doesn't even need a discussion.
Pinkie Pie can apparently teleport, has hammer space, and has her pinkie senses.
Rarity is pretty, and Applejack is hardworking. Best super powers ever!