Sosuke Aizen's (Bleach) power and fighting skills allow him to defeat the strongest Shinigamis, even Genryusai Yamamoto with his tactical genius.
Genryūsai Shigekuni Yamamoto (Bleach) was considered to be the strongest Soul Reaper in existence for the last millennium. Even without his powers, he could still obliterate a powerful Arrancar with is bare hands.
Kenpachi Zaraki (Bleach) is one of the most badass Shinigami, able to defeat almost any opponent with sheer strength and determination. He is badass the point that when a reality warper tried to make himself more badass than Kenpachi, he found that this was literally impossible.
Goku (Dragon Ball franchise) is most famous for overcoming any obstacle, no matter what, through sheer determination and hard work; culminating in him reaching a state of being beyond even gods.
Vegeta (Dragon Ball franchise) has pulled many badass feats, but his crowning achievement comes from defeating a God of Destruction through sheer determination.
Vegito (Dragon Ball franchise) is the fusion of Goku and Vegeta, and therefore is one of the most badass fighters there is by default.
Broly (Dragon Ball Super)
Issei Hyoudou (Highschool DxD) as Diabolus Dragon Form.
Like most Abnormals, Medaka Kurokami (Medaka Box) can achieve incredible feats, such as catching cascade of bullets with her mouth.
Raizo (One Piece) is an awesome ninja.
Germany (Axis Powers Hetalia) can break a spoon with his bare hands, along with other things.
Guts, the Black Swordsman (Berserk) is the absolute master of his own fate.
Jotaro Kujo (JoJo's Bizarre Adventure) is an extremely cool individual, able to keep his composure in even the direst of situations. A gambler trying to steal your soul? An evil assassin holds your granddad as a hostage? A immortal vampire trying to kill you? CALL HIM.
Saitama (One-Punch Man) vs. the… never-mind.
The Worst Generation (One Piece) are 12 most powerful and fearsome pirates of the modern era who are regarded by the World Government to be their worst nemesis for the immense chaos and disorder they have caused against the world…
…Capone Luke "Gang" Bege, the genius master tactician of the Fire Tank Pirates who has defeated the most powerful enemies with his tactical genius alone…
…Trafalgar D. Water Law, the captain/doctor of the Heart Pirates who is feared as the Surgeon of Death…
… the Magician Basil Hawkins the oracle leader of the Hawkins Pirates…
…the Roaring Tide Scratchmen Apoo, the DJ musician/captain of the On Air Pirates…
…the sadist daredevil captain of the Kid Pirates, Eustass "Captain" Kidd…
… Monkey D Luffy, the youngest of the Worst Generation who has miraculously committed numerous near impossible feats that have shook the Three Great Powers of the world to the core…
The Straw Hat Pirates (One Piece)
… "Blackbeard" Marshal D. Teach Captain of the Blackbeard Pirates, who has achieved what no one else could ever do, overthrow Whitebeard one of the Yonko of the New World, steal his Gura Gura no Mi powers and take over his position as one of the Yonko.
Edward "Whitebeard" Newgate (One Piece) truly lived up to his reputation as "World's Strongest Man". Even in his advanced age, ill and far from his prime, it still took a lot to eventually kill him.
Kaido (One Piece), without any doubt, truly lives up to his reptutation as "The Strongest Creature in the World".
Charlotte Katakuri (One Piece) is a legendary figure amongst the Big Mom pirates for his sheer badassery, skills, and professionalism. Having never lost a single fight from the day he was born until he was finally defeated by Monkey D. Luffy, Katakuri was the rock that held up the Big Mom Pirates.
Fairy Tail members (Fairy Tail) overcame tough trials making them very famous among other guilds, if not the most famous one and is feared of their strength and their accomplished goals. to the point of defeating the immortal Zeref.
Shin of the Hi Shin Unit (Kingdom) has done the very impossible for somebody who was originally a servant and a slave. Killing over 20 enemy soldiers, destroying a war chariot he never saw before, diving head first into a sea of enemy soldiers just to save his fellow squad mates and killing a enemy general just on his first campaign.
Ou Ki, the Monstrous of Qin (Kingdom) was one of the most dominant military figures of his era, numbering victories on the battlefield against many formidable foes. At the time of his death there was not a single general as hated by the masses as him and was rumored to be the strongest of Qin's Six Great Generals.
Kan Ki, the Beheader (Kingdom) is a genius prodigy at warfare, never even formally studied strategy yet has never lost a battle because of his unique unorthodox tactics. Just by dedicating entire day of doing nothing he was able to throw everybody, even own allies, off just to bait and lure the enemy commander out of hiding (not to mention pissing everybody off, too).
Ri Boku of the Three Great Heavens (Kingdom) is a Great General of the Heavens from the State of Zhao, before he made a name for himself he was mostly known for subduing the Xiongnu threat to the north which constantly raids the northern part of Zhao, a feat which no other Zhao general had achieved before.
Hou Ken, the Bushin (Kingdom) is considered a walking manifestation of calamity and violence.
Having been a full fledged martial artist since the age of 3, Kenshirō Kasumi (Fist of the Blue Sky) wandered the Shanghai underworld crippling or killing those he would fight which eventually earned him the moniker of Yánwáng (King of Death).
Kenshiro (Fist of the North Star) is ultimately regarded as the world's strongest man. His mastery of the greatest martial art the globe, The Hokuto Shin Ken (Big Dipper God Fist), has garnered him titles such as the Savior of The Century's End.