If I could describe RD in only a few words, I'd say she's a bit overrated and over confident. And a ***** at some points, and irritating. I dunno she just gets annoying sometimes. That's just me though, everypony's entitled to their own opinion.
Extroverted, reckless and plenty confident, but ultimately good natured, well meaning , brave and loyal. I sure wouldn't mind having a friend like her.
...Hang on. Let me find someone to translate that. Can you do it Boris? Rainbow Dash is a Tomboy that's all mouth but generally, little trousers in terms of her confidence.
Loyal, I guess. Yeah, I went there. It's pretty easy to describe her; she, like the other main characters, is usually written to be very straightforward.
Blue streak speeds by Rainbow the Pony Too fast for the naked eye Rainbow the Pony Rainbow! She's cool and cute! Rainbow! She's got attitude! Rainbow! She's the fastest thing aliiiiiiiive! Look out when she comes through Rainbow the Pony Don't doubt what she can do Rainbow the Pony Rainbow! She can really move! Rainbow! She's got attitude! Rainbow! She's the fastest thing alive! She's the fastest thing alive! She's the fastest thing aliiiiiiiiiiiiiiive!!!!!
I will also say that I think Rainbow Dash kinda tends to get picked on a lot more than any of the other Mane Six, though she does also seem to have a decent crowd of loyal fans.
