Rainbow Dash, Barrier Breaker

You know how in anime, when the main character is in a pickle, against all odds, they rise up to the challenge, breaking all their previous barriers to do so.

For the record, no, I wasn't particularly inspired by any anime in particular.

Had a bit of trouble with the effect here, for a while it didn't grant an extra combat step, however that meant that it would be pointless if it died when it was attacking, even though thats what i would want to see the most. The extra combat step not only eliminates that issue, but also makes it even more powerful when it triggers! Notice that the bonus lasts until YOUR last end step, meaning that if it dies during an opponents turn, it stays fat until your turn, though no extra combat steps will be had. Vigilance here was added in order to stop people from wanting to keep it back as a blocker, which seems very likely in a lot of circumstances.

Seems like a real pain to play against, even without the effect, its still pretty reasonable, the effect means that killing it is dangerous unless they have a way to deal with the 5/5 double striking trampler, obviously, vigilance makes this even more of a problem, and of course, evasion and first strike is always powerful (although, first strike may sometimes be a negative) Although there are a variety of ways to deal with it, its still certainly dangerous if mishandled.

The effect seems like it has a lot of potential for very exciting plays, and very strategic plays. It works excellently as a finisher, and has some powerful interactions with some cards, so it can end up being very memorable for players. Besides giving your opponent a headache when decided how to deal with in combat and with removal, it also can be tough for the user, when they need to decide whether throwing it into combat when it will die is a good idea, or whether its better to wait on it and develop more of an offense.

Besides the potential as an end of curve for aggro or midrange, you could pretty easily build around it in a reanimator with black. Consider that if you reanimate it, then sacrifice you get 2 extra combat steps, and a fat creature to beat faces in during those combats.

EDIT: Since it seems so powerful, and its not at all what i want people to do, made requiring a -1/-1 counter part of the ability, along with requiring her to still be in play to grant an extra combat, mainly to solve issues with playing multiples of her and them both dying from legend rule.