Meruem (Hunter X Hunter) possesses incredible pain tolerance, to the extent that he can rip off his own arm without batting an eye.
Roronoa Zoro (One Piece) possesses incredible endurance to pain, able to withstand being stabbed in the chest and even taking on all of Luffy's pain and fatigue.
Even in his childhood Vinsmoke Sanji (One Piece) could withstand being brutally bullied by his three superhumanly strong brothers...
...by adulthood, Sanji is tenacious enough to survive the most powerful attacks from the strongest enemies.
Oars (One Piece) is a zombie, and therefore cannot feel pain as its pain receptors are no longer functioning.
Whitebeard (One Piece) was able to endure having half his face burned off and a hole punched through his chest and continue fighting with no less might.
Hody Jones (One Piece) overdosed on Energy Steroids, causing insanity that overrode pain.
Hajrudin (One Piece) can withstand tremendous physical pain such as the brutal fractures of his arm and leg…
and still smash Machvise into the highest Heavens.
Due in part to a charm placed on her, Kahlua Shuzen (Rosario + Vampire) is able to neutralize her ability to feel pain; however, this also works against her, as she has no way of knowing how much damage her body takes until it's too late.
Gintoki Sakata (Gintama) completely ignored all injuries and pain inflicted upon himself to continue fighting viciously, due to his low regard for his own life.
Kagura (Gintama) once gave in to her Yato instincts, ignoring all injuries to fight on.
Kamui (Gintama) can easily ignore his injuries due to his Yato blood, especially if he is consumed by its instincts.
Killua Zoldyck (Hunter x Hunter) has been trained via torture since birth to have extreme tolerance for pain, electrocution and poisoning.
Yukishiro Enishi (Rurouni Kenshin) has mastered mind over body, not feeling the negative effects of pain if his body does not recognize it.
After enduring brutal torture for ten days straight, Ken Kaneki (Tokyo Ghoul) has built up such a high pain threshold that he barely reacts to such things as having his leg broken in multiple places.
Kanon Ozu (Coppelion) cannot feel pain (or anything) due to the electricity that courses through her body numbing it entirely.
Gatasubal (Yu Yu Hakusho) does not feel pain due to its creator made it so.
Minoru Kamiya (Yu Yu Hakusho) cut off the analeptic chemicals, preventing himself from feeling pain.
As he is just a soul inhabiting a suit of armor, Alphonse Elric (Fullmetal Alchemist) cannot feel any pain.
Checkmate (Ultimate Muscle) was put through intense training as a child to render himself unable to feel pain.
Cyborgs such as Motoko Kusanagi (Ghost in the Shell) are able to voluntarily shut their pain receptors off.
Due to the physical strain and abuse on his body when he used his strength as a child, Shizuo grown to the point he longer feels it.
Because of his strong endurance and representing violence, Kenpachi has a high tolerance to pain and ignore fatal strikes when fighting Ichigo and Nnoitra.
Mana took an axe strike from Masato to protect Yuta, showing no flinching from pain.
Having been horribly tortured in the past, Chimera (Marchen Awakens Romance) has built up an unusually high tolerance for pain. Compared to her past, even the pain of walking through boiling water is something Chimera can easily ignore and even gain pleasure from.
After years of training, Saitama (One Punch Man), who was able to suppress his pain even before he became a hero, has rendered himself unable to feel almost any pain.
Due to the experiments of the first Kiznaiver project, Agata Katsuhira (Kiznaiver) can no longer feels physical pain.
Nomura Fudo (Busou Shoujo Machiavellianism) has extremely strong endurance to physical pain.