It's normal to root for the underdog and little exemplifies this more than the idea of a David Vs Goliath fight. This concept is where a smaller, less apparently strong individual is pitted against a larger, often muscle-bound giant and the underdog comes out on top. It's become something of a trope within media, but it has because of how successful the idea is.
Anime is no stranger for writers to create wild and crazy power sets for characters, but accordingly have equally overwhelming size or strength in the villains that the heroes face. Sometimes this is done in all seriousness, but it can also be played on for humor by subverting the trope. These are some of the best examples of David Vs Goliath fights in anime.
This article may contain spoilers
10 My Hero Academia
In the world of My Hero Academia, the David Vs Goliath battles can be both figuratively or literally. Heroes or villains have quirks from the simple, unassuming Best Jeanist who is capable of manipulating clothing to the over the top and overpowered quirks of villains such as Gigantomachia.
Anyone who enters the world of hero or villain work may end up fighting someone far more powerful or larger than themselves and this is never more exemplified than through Deku, the protagonist who starts as a small, teenage boy and uses his powers to fight villains with more experience and who are substantially bigger than him.
9 Fist Of The North Star
In a post-apocalyptic world, humanity survives as best it can against the roaming bandits and strange mutated warriors. It is not unusual for the protagonist Kenshiro to find himself fighting someone larger or more skilled than himself and becoming the victor.
The opponents he fights can seem large in terms of the normal human limits and appear slightly larger than the protagonist, however the setting permits for some rather large physical characters to appear in combat that tower over others, though in these instances, their actual power is often showed to be less impressive.
8 Dragon Ball
While Son Goku would go on in later series to follow his fighting instincts and fight those more powerful than himself, the true David Vs Goliath fights happened when he was only a child. A good portion of the humor of Dragon Ball came from villains underestimating the child hero who often barely reached their knees.
Dragon Ball shows Goku fighting androids, ninjas and combatants whether out adventuring or in the world martial arts tournament. The series shows the young man's power early on, and he defeats multiple enemies time and again, even putting one of them on the moon (which is later destroyed by Master Roshi).
7 Battle Angel: Alita
While the deadliest cyborg in the city of Scrapyard, Alita herself is only around 5 feet tall. Her training and history as a military cyborg, along with her knowledge of the Martian martial art, Panzer Kunst make her far more deadly a fighter than the natives who live within the city.
Alita's and Daisuke Ido's roles as hunter-warriors are to act as bounty hunters for criminals within the city of Scrapyard. These criminals have often modified themselves to be bigger and stronger than the average human. Despite their sizes and skills, both Alita and Ido's skills allow them to defeat villains who would otherwise crush them.
6 One Punch Man
Saitama is the most powerful hero of all time, so powerful he can defeat any enemy with one punch. Saitama does not look much different to any other human except for his cape and bald head, but he often takes on beings that are taller than skyscrapers.
While One Punch Man does not take itself seriously, more or less every fight puts Saitama at the obvious, visual physical disadvantage against his opponents. The series then reveals the true power of Saitama and, as the name of the series suggests, they are all defeated with one single attack.
5 Pokemon
Pokemon is a series that suggests that size is largely irrelevant when it comes to fighting within a Pokemon match. The real power comes from the connection of the trainer and their friend, though being bigger and having a type advantage can certainly can help.
Despite his size, Pikachu is a powerhouse when it comes defeating the opposition. With the power of electric moves, Pikachu has defeated Pokemon far larger than himself and has taken his companion, Ash across the world and defeated numerous gyms to even become the pokemon world champion.
4 Berserk
Berserk's protagonist Guts, is a human, though one who has trained to the peak of human physicality and is a master swordsman. It's a good thing that he is so strong as Guts' primary opponents are apostles. These are beings who were once human but sacrificed a part of their humanity for the gain of superior powers and strength.
Every apostle that Guts fights is vastly more powerful than he is and only through the use of his skills, technology and the incredibly large sword, The Dragon Slayer is he able to defeat them. Almost every battle he fights is a David Vs Goliath fight as he struggles against death with every fight
3 One Piece
As the best-selling manga in history, One Piece's main hero is Monkey D. Luffy and his Staw Hat Pirates in their search for the One Piece, so that he can declare himself the king of all pirates. After consuming a Gum Gum Fruit, he finds his body is made of rubber and, he uses these to fight against those who stand in his way.
Many of the battles that Luffy finds himself engaged in are with villains much larger than himself. Though they are often highly capable and powerful in their own right, Luffy manages to fight them one by one and beat them down by using his wits, skills and of course, a good punch or two with his rubber fists.
2 Assassination Classroom
Within class 3E within Korosensei's Assassination Classroom, the children who take the classes are trained to take down targets tougher than themselves. As the class consists of younger teenagers, this consists of most of the people that they encounter.
The smallest and apparently weakest is Shioto Nagisa, and while he may not be an intimidating character simply from how he looks, he becomes the deadliest of all the members of the classroom. In his lessons he meets adult teachers or genuine mercenaries, but this particular David manages to defeat each Goliath that appears.
1 Attack On Titan
The gigantic walls that surround the last survivors of humanity protected everyone from the dangerous titans that lurked in the world outside. Although more is learned about the world as the series carry on, that initial description reveals the true horror of the David Vs Goliath fights that take place within the anime.
Titans vary in size with the smallest being roughly the size of a house and the largest being significantly larger. While Eren Jaeger has powers that enable him to fight these monsters, every other human only has technology and skill to defeat these literal giants, and often they struggle and fail.