Anime series where the main character seems destined to defeat their opponents without conflict are quite often uncompelling. Sure, One-Punch Man makes it work, but not every anime can be One-Punch Man. In most cases, underdog characters who don't seem like they can possibly win are the ones that get viewers invested. It may seem like they won't ever achieve their dreams, but when they finally do, victory never tasted sweeter.
If they fail, it's tragically heartbreaking, as their will to power makes viewers want to see them persevere. The best underdog anime characters can make fans feel like they accomplished something alongside them, as an unexpected victory is universally gratifying.
Rock Lee starts off life with a disadvantage that most characters in Naruto don't have: he can't use chakra, the life force that allows ninja to use ninjutsu and genjutsu. This means that he can only use taijutsu, which amounts to real-life martial arts.
In a world where being able to run up a wall by concentrating the chakra in your feet is a standard skill, and where abilities like controlling fire and cloning yourself are normal, Lee has to work double-time if he wants to be a ninja. Things seem hopeless at first, but through tireless training, he becomes so good at taijutsu that he can hold his own against ninjutsu users.
Noragami's protagonist Yato is a low-status deity who is trying desperately to collect enough money from his followers to buy himself a shrine, which he needs in order to be recognized as a real god. He does this by offering to do odd jobs for five yen apiece, and he saves his earnings in a jar. Needless to say, it's not really working all that well. While watching Yato struggle to achieve a goal that seems impossibly far out of reach, viewers can't help but root for him out of sheer pity.
Shoyo Hinata of Haikyuu!! wants to be amazing at volleyball, but that's easier said than done when you're only 5'4". While the kid can jump exceptionally high, that's not necessarily enough to make up for his height in a sport that centers on getting a ball over a net. Despite this setback, Hinata works his butt off, and it's hard not to want the little guy to achieve his dream.
At first glance, Vegeta of Dragon Ball Z might not seem like an underdog. After all, he's one of the most powerful beings in the galaxy. That said, he keeps falling short of one of his major goals: defeating Goku — or as he calls him, Kakarot — once and for all. Unfortunately for Vegeta, this goal remains frustratingly out of reach for the Saiyan prince; the one time he does actually come out on top, he's thrashed by Goku's friends soon afterwards.