Dash looked up at the scarred sky, the destructive wake of her sonic rainboom used in combat. Although she had downed much of the enemy - these strange, two legged creatures and their flying machines - more were on their way, carving out an ever widening path of destruction across Equestria as they shot pegasi out of the sky and rained fire on the earth-bound ponies below.
 
All of her wingponies either dead or lost in the disarray of combat, Rainbow Dash grimly realized at that moment she was the last line of defense between Ponyville and the aerial armada of the ruthless invaders. This was what she had always imagined she wanted as a filly - to be the hero that saves the day.
 
But as the death and carnage of total war had taught her in these last few days, heroes can’t always save the day.
 
At best, she could hope to delay them and give her friends time to fortify their defenses and evacuate the town’s citizenry. Such an action would most likely cost her life.
 
But she was the element of loyalty - and there was no greater act of loyalty than to lay down one’s life for a friend.
 
Gritting her teeth and eyeing the approaching craft in her bloodied gaze, Dash only grunted “Bring it.” She shot off, convinced this would be her final flight - Dash vowed to make it her greatest.

Looks cool.

the aftermath of Sonic Rainboom in battle.