You know, this is how I imagined what Twilight would look like if she released her hidden potential. Sometimes in the show, when Twilight experiences extreme emotion, part of her power goes temporarily out of control, but she holds those feelings back enough for her friends to be safe. But, say, if some sort of muscle-bound brute had injured all of the gang to the point where they couldn't move, including Spike, Twilight's pushed over the edge and her magic bursts forth.
Actually, I had in mind more along the lines of Twilight learning to let her anger free but not letting it take control of her. Seeing that Spike is hurt the most, she assumes he's dead, and realizes that her whole life, she held back her feelings because she didn't want to hurt anypony, but it was because of the very responsibility to protect her loved ones that she became angry in the first place.
I take back what I typed about Spike being hurt the most, the bad guy actually just blasts him into the horizon, and after Twilight defeats the brute, it turns out Spike wasn't even close to dead. Of course, there's still a teary grievance after she finds him, and then he wakes up after her a few of her tears touch his tongue.