>>42275635
if we're ranking kindness, Derpy is above Luna who was quoted to have murdered several of her therapists purely out of anger. Trixie is also probably above Soarin since she really was one of the most empathetic ponies despite her evil heart, even not wanting to kill mary but understanding that letting her live would burden Twilight.

Arguably, there is Coco who's possibly above Cadence but behind WallFlower who has an actual pure heart as Mary goes on to show. So WallFlower is the kindest pony of all in canon