In order to attain longevity, Honest (Akame Ga Kill!) has rigorously trained his body to complete perfection...
...gaining immense strength and fighting skills to single-handedly overpower a Teigu user.
Having been trained as a mercenary since age six, Guts (Berserk) possesses incredible physical capabilities, able to easily wield a massive 400-lb sword with one arm, move faster than the eye can see, and survive wounds that would be fatal to a normal man.
The Vizards (Bleach) underwent hard training to fully control their new found Hollow powers after being forcefully modified into Hollow Hybrids.
Ikki Kurogane (Chivalry of a Failed Knight) has extensively trained his body to make up for his lack of magical capacity, allowing him such feats as removing his physical limiters to fight at full strength.
Son Goku (Dragon Ball series) was taught by Grandpa Gohan the basics of martial arts, by Korin in endurance and opponent anticipation, by Master Roshi in Kame-Sennin Ryu to push his body to superhuman levels, by Mr. Popo and Kami in ki sensing, mediation, precision, and Bukūjutsu, and by North Kai in ki training, the Kaio-ken and Spirit Bomb.
Master Muten Roshi (Dragon Ball series) achieved superhuman status through training, to the extent that he was once hailed the strongest man in the world.
Though nowhere near the Z-Fighters' level, Hercule (Dragon Ball series) is nonetheless more powerful than an ordinary human thanks to his training, able to pull off such feats as moving faster than the eye can see
, pulling a line of four buses several feet with his bare hands, and surviving hits from Perfect Cell and Kid Buu.
Through four months of rigorous training, Frieza (Dragon Ball) became the first of his kind to awaken the Ultimate Evolution.
Once fairly weak, Jiren (Dragon Ball Super) trained himself extensively, eventually becoming so powerful that not even a God of Destruction could defeat him.
Even without his Devil Fruit powers
, Monkey D. Luffy (One Piece) possesses incredible strength and combat skill as a result of the training regimen his grandfather, Garp put him through.
Saitama (One-Punch Man) broke through his human limitations and achieved unbelievable strength and abilities considered impossible through an extensive training regimen.
Those who practice Hokuto Shin Ken (Big Dipper God Fist) (Fist of the North Star) train to unlock and use their bodies' full muscle potential.
Genkai (YuYu Hakusho) is an incredibly skilled martial artist known to humans and demons alike. Her personal Reihado-ken fighting style allows her to revert her body its peak. She is also a harsh teacher with grueling, but beneficial, training methods.
Yusuke Urameshi (YuYu Hakusho) went through hard training under the teachings of Genkai, but in turn was able to learn the Spirit Shotgun, Spirit Wave, and had his Spirit Energy greatly improved by the aid of her Spirit Cuffs.
Shinobu Sensui (YuYu Hakusho) is a master of the Resshūken fighting style, which is said to be to be the strongest, most elegant, school of martial arts in existence. In addition to this, he was able to master the Sacred Energy
with only six years of discipline instead of the usual forty.
Even in old age, Walter C. Dornez (Hellsing) possesses superhuman speed and acrobatic skills due to years of training and experience.
Akisame Koetsuji (History's Strongest Disciple Kenichi) has trained his body to that point that he has absolutely no unnecessary/useless muscle, as every single inch of his frame is composed of only pink muscle. Granting him nearly superhuman skills equal to the Elder.
While originally the weakest, Issei Hyodou (Highschool DxD) became the strongest reincarnated Devil of his generation through constant and rigorous training.
Cao Cao (Highschool DxD) has trained his body and fighting skills to utmost perfection, making him strong enough to defeat the most powerful supernatural beings.
Sword Emperor Elline (Sekai no Owari no Encore) attained his legendary swordsmanship skills through extremely hard training.
After two years of extremely rigorous training, Monkey D. Luffy, Roronoa Zoro and Vinsmoke Sanji (One Piece) became tremendously powerful, able to survive the dangers of the New World.
Having received the harshest military training for gifted mamodo children, Zeno (Zatch Bell!) is able to completely overpower and humiliate the majority of mamodo fighting in the battle to become king.
After entering the Chess Pieces, Chimera (Marchen Awakens Romance) honed her skills to near perfection. In less than 6 years, she was promoted to the exclusive rank of Knight class ranking 4th out of the 13.
Due to reincarnating, having an extremely large mana capacity and training himself since he was an infant, Vandalieu (The Death Mage Who Doesn’t Want a Fourth Time) gained the strength to defeat individuals on par with S-rank adventures and Pure-Breed vampires at the age of 8.