Anal fissure that is extremely painful. What is the fastest treatment for this?

Depends. First line treatment is a high fiber diet, plenty of fluids and possible a laxative to keep your bowel movements soft. Warm baths. If persist, prescription antispasmodic cream if persists, Botox or surgery in form of sphinterotomy the above order is also depended on the severity, persistency, recurrence and appearance of your fissure if your symptoms are severe and persist see a colon and rectal.