[The Loli Patrol]

I think D. Gray Man is indeed underrated but I don't think its because of the show itself, it follows the typical guy is weak perhaps through a plot point into guy becomes strong again perhaps through a plot point or just general fight that causes him to push himself, And through the turn of events that we call "character development" you get your finished character with op moves doing op stuff aka finding out his background, modes etc. Now you may be asking yourself, why is he saying all this? Well i think one of the things that makes a series underrated is a stray from the path and like you have probably seen he doesn't stray from the "path", so that leaves us with the bigger culprit the reason D. Gray Man is underrated is because the show was released at a time where a lot of new and interesting ideas were developing and sadly you cant build a loyal fanbase when 12 other shows are starting up and their manga or light novels just have more content. I think a lesson to be learned is just that you dont start up your anime in the middle of a season you do it at the beginning or the end.