Note: This story is the second part of a trilogy - links can be found at the bottom of the description.

Following a Unicorn victory in the crippling Harmony's End War, Rainbow Dash has turned from soldier to activist, advocating peace and tolerance in the hopes that Equestria can avoid another horrific war. But the Unicorns have other ideas, and are crushing the other two races under their collective heel. Dash is tough, and is willing to persevere, despite growing public unrest and repeated attempts by the Unicorns to shut her up for good... until something happens that nearly breaks her, something that sends her on the warpath, sworn to destroy the Unicorn regime, once and for all.

Fire, Harmony's End part 1:
http://www.fimfiction.net/story/45314/Fire-%28Harmony%27s-End-Part-1%29
The Cross, Harmony's End part 3:
http://www.fimfiction.net/story/45606/The-Cross-%28Harmony%27s-End-Part-3%29