Needs moar Flandre. :V
Common State of Innocent Violence, by Crow's Claw The first Touhou remix I ever heard. It seems to evoke Flandre's raw destructive power more than her childlike innocence.
Heart Under Blade, by Kokuyasou/Black Night Funeral A great song by one of my favorite arrangers. I like it for the same reasons as Common State of Innocent Violence, and it has basically the same tone.
The One Who Inherits the Scarlet Craze (紅い狂気の継承者), by ARA Not much to say about it, but it's good.
U.N. Owen Was Her?, by Cool&Create I like it more as a song than as a representation of Flandre's character, personally.
U.N. Owen Was Her?, by 砂塵音樂室 I like it for the same reasons as Cool&Create's arrange, but I particularly like what they did with the portion from 0:17 to 0:29.
悪魔の妹と4台のピアノのための極めて破壊的な狂騒曲, by Xe One of my favorite U.N. Owen arranges, it perfectly demonstrates the innocence, anger, hopefulness, sadness, and raw power that I feel form Flandre's character.
Unknown? by Mistyhaze The only song by Mistyhaze that I actually like. It evokes the same feelings as the previous song in the list, I think, but in its own, unique way.
緋色月下、狂咲ノ絶 by EastNewSound I have mixed feelings about this one: I really like it, but I can't decide if it fits Flandre's character or not. Seems like it does to an extent.
Sweets Time Midnight Nearly my favorite arrange of Flandre's theme, and a perfect representation of Flandre's character. There isn't much more to say.
U.N. Owen Was Her? by TAMusic My favorite version of U.N. Owen Was Her?. It's really just perfect in so many ways.