Number 5 HAN DAE-WI from one of the most lesser known mangas he is part of God of high school people often think he is weak do to his recent injury of losing an eye and is destined to soon die but even then he was the original one to go against Jin mo ri who is a god and give him a real fight.
4th Rogue and Sting these to share the spot as they r both just bad in the series they had so much potential but are both beaten badly by natsu and gajeel and even now do not compare to the other dragon slayers they will probably be left behind as weak characters in the fairy tail universe but they sure r a fan favorite.
Number 3 genoes yes he isn't really weak probably being one of the strongest anime characters ever but in his universe he just gets destroyed in every fight he's been in either his teacher Saitima helps him out or he gets destroyed.
Number 2 kurapika OMG i love this character let me say this now but people don't find him as good as he should be being left out of all the other action after the yorknew arc and only defeating one major character in the series he will probably always be out shined by Killua and Gon.
Number 1 Sanji ALL RIGHT I'M A GET A LITTLE BIT ANGRY ABOUT THIS ONE BECAUSE AGAIN I LOVE THIS CHARACTER. Sanji this badass right here is always considered weak yes he is one of the strongest members in the straw hat crew but what else has he really done yeah before the time skip he was pretty good being able to fight the so called third strongest of each group but let's be honest most of the fights he does r jokes Mr.2 kurobi the invisible guy, sorry forgot his name but most of his fights r either one sided or just stupid again i love this character but even now after the time skip sanji has done nothing like usopp has done way more then sanji in the past arcs then him i hope he gets some time to shine in the new arc though.