Character: Allen Francis Doyle
Source: Angel (TV show)
Condition: chronic headaches

Character: All Might
Source: My Hero Academia (anime)
Condition: respiratory damage
Read More: "All Might and the Importance of Rest," Super Sick chapter 4

Character: Amanda Brotzman
Source: Dirk Gently's Holistic Detective Agency (TV show)
Condition: Pararibulitis
Read More: Super Sick chapter 10

Character: Ava Starr, a.k.a. Ghost
Source: Ant-Man and the Wasp (movie)
Condition: chronic pain

Character: Aza Ray
Source: Magonia by Maria Dahvana Headley (novel)
Condition: lung disease
Read More: Super Sick chapter 2

Character: Cloud Strife
Source: Final Fantasy VII (video game/movie)
Condition: Mako poisoning and Geostigma
Read More: "Cloud Strife and Depression," Super Sick chapter 6

Character: Collem West
Source: The Blade Itself by Joe Abercrombie (novel)
Condition: chronic headaches

Character: Cyra Noavek
Source: Carve the Mark by Veronica Roth (novel)
Condition: chronic pain
Read More: Super Sick chapter 11

Character: Eliwood
Source: Fire Emblem: Blazing Sword & Sword of Seals (video games)
Condition: debilitating illness

Character: Frodo Baggins
Source: The Lord of the Rings by J.R.R. Tolkien (novels)
Condition: chronic pain from a knife wound

Character: Greer Sonnel
Source: Star Wars: Bloodline by Claudia Gray (novel)
Condition: Bloodburn syndrome

Character: Gregory House
Source: House (TV show)
Condition: chronic pain from muscle death
Read More: Super Sick chapter 3

Character: Inara Serra
Source: Firefly (TV show)
Condition: unnamed illness

Character: Izumi Curtis
Source: Fullmetal Alchemist & Fullmetal Alchemist: Brotherhood (animes)
Condition: chronic illness from missing organs

Character: Jane Foster, a.k.a. Thor
Source: The Might Thor (comics)
Condition: cancer
Read More: "Jane Foster and Worthlessness"

Character: Kaori Miyazono
Source: Your Lie in April (anime)
Condition: ALS

Character: Konno Yuuki
Source: Sword Art Online (anime)
Condition: AIDS

Character: Laura Roslin
Source: Battlestar Galactica (TV show)
Condition: cancer
Read More: "Laura Roslin & Perseverance"

Character: Lincoln Rhyme
Source: The Bone Collector by Jeffery Deaver (novel)
Condition: quadriplegia
Read More: Super Sick chapter 13

Character: Morinth
Source: Mass Effect 2 (video game)
Condition: a genetic disorder where she kills anyone she mates with

Character: Raistlin Majere
Source: Dragonlance series by Margaret Weis and Tracy Hickman (novels)
Condition: unnamed illness

Character: Raoden
Source: Elantris by Brandon Sanderson (novel)
Condition: cursed so that injuries never heal
Read More: "Raoden and Chronic Pain"

Character: Raven Reyes
Source: The 100 (TV show)
Condition: chronic pain from nerve damage
Read More: "Raven Reyes & Pressing On"

Character: Remus Lupin
Source: Harry Potter and the Prisoner of Azkaban by J.K. Rowling (novel and movie)
Condition: lycanthropy (i.e. he's a werewolf)
Read More: Super Sick chapter 7

Character: Rhys
Source: Fire Emblem: Path of Radiance (video game)
Condition: unnamed chronic illness
Read More: Super Sick chapter 5

Character: Sand dan Glokta
Source: The Blade Itself by Joe Abercrombie (novel)
Condition: chronic pain

Character: Shannon Rutherford
Source: Lost (TV show)
Condition: asthma

Character: Stephen Strange
Source: Doctor Strange (movie)
Condition: damaged hands
Read More: Super Sick chapter 1

Character: Tali'Zorah
Source: Mass Effect 2 (video game)
Condition: weak immune system and dextro-amino acid chirality

Character: Thane Krios
Source: Mass Effect 2 (video game)
Condition: Kepral's Syndrome
Read More: Super Sick chapter 12

Character: Tony Stark, a.k.a. Iron Man
Source: Iron Man and other MCU movies
Condition: heart condition

Character: Wade Wilson, a.k.a. Deadpool
Source: Deadpool (movie and comics)
Condition: cancer
Read More: "Wade Wilson and Shame"

Character: Cinder
Source: Cinder by Marissa Meyer (novel)
Condition: she's a cyborg

Character: Harper
Source: A Curse So Dark and Lonely by Brigid Kemmerer
Condition: cerebral palsy