Mimihagi (Bleach) governs stagnation, and was due to its powers that it stopped the progress of Ukitake's fatal lung disease, allowing him to live on, though not without chronic pains. He partially compensates this with his own reiatsu to suppress the pain.
Papillon (Buso Renkin) managed to suppress the fatality of his terminal disease by becoming a homunculus, but due to him using an incomplete embryo to achieve the transformation, he could not completely cure himself and still suffers from chronic pains.
Lex Luthor (DC Comics) wore a chest plate to staunch the Kryptonite poisoning-induced cancer from worsening, unaware that he has been cured by Brainiac until later, thus negating the need for the plate anymore.
Nathan Summers/Cable (Marvel Comics) uses most of his psychic power to suppress the techno-organic virus in his body, preventing it from spreading.
While bonded to him, the Venom symbiote (Marvel Comics) suppressed the effects of Eddie Brock's terminal cancer, keeping him alive.
Dr. Dayton King (No Ordinary Family) requires a special serum not only to keep himself alive as well as to resist the cancer he had 18 years ago.
Doc Q (One Piece) was born with an incurable fatal disease, yet he could exert himself to fight the most intense battles as a member of the Blackbeard Pirates.
Edward Newgate (One Piece) through his immense willpower and powerful vitality could suppress the debiliating symptoms of his deteoriating health to fight the entire marine forces, even when dead, he died standing.
Crocus (One Piece) is considered the greatest doctor of his time, being able to halt even the deterioration of Gold Roger's incurable disease.
After Sonic the Hedgehog (IDW's Sonic the Hedgehog) was infected by Dr. Eggman's MetalVirus...
...he discovered he could burn it off and stop it from spreading through his speed...