Colonel Volgin/Man on Fire (Metal Gear Solid V: The Phantom Pain)
Dollotron (DC Comics)
Saya (Saya no Uta)
Touhou Fuhai (Rosario + Vampire)
Tsukune Aono (Rosario + Vampire)
Chase Young (Xiaolin Showdown)
Frost (Dragon Ball Super)
Ghost ÄRMs (Marchen Awakens Romance)
Sosuke Aizen (Bleach) has done immense research on Hollows, allowing him to give Shinigamis's Hollow powers such as a Hollow Mask and even a Resurrección.
The Vizards (Bleach) were among the numerous Shinigamis who fell victim to Aizen's Hollowfication experiments, through extensive training they attained full control over their Hollow powers.
As a result of an experimental medical procedure, Peyton Westlake (Darkman) no longer has any nerve endings, rendering him immune to physical pain, while also causing adrenaline to flow through his body unchecked, increasing his physical attributes and leaving him emotionally unstable.
Professor Pyg's Dollotrons (DC Comics) were once-ordinary people who were modified by extensive surgery.
Frost (Dragon Ball Super) has modified himself to possess poisonous stingers in his wrists.
Doc Benton (Supernatural) regularly transplants others' organs and body parts onto himself.
In addition to replacing his left hand with a mechanical one and installing a clockwork heart, Karl Ruprecht Kroenen (Hellboy/BPRD), suffering from severe "surgical addiction," performed surgery on himself to remove his own eyelids, lips, and finger and toe nails.