I used bleach in wrestling a couple times. I used cotton swabs to apply it to the rings, burns like a bitch, but it kills ringworm basically on the first shot. Leaves a rag nasty scar though.
I usually used straight bleach, but some of the other guys diluted 100:1 or 1000:1 and they said it hurt less and scared less, but it took more treatments to get rid of (we applied after every shower, so about 2 or 3 times a day).
That said, as I went through college, I learned that bleach usually contains some levels of caustic, which can penetrate deeply and cause permanent nerve damage, plus some cheaper bleaches will contain traces of chloride solvents that can penetrate the skin and deteriorate your bones...
So yeah, like one of the other guys said, bleach is the nuclear option. Basically, we only used it if we had something big coming up, since the prescription method only holds you out for 7 days anyway, but our rule in Kansas at least was that the sores had to be essentially healed, not just scabbed, so it couldn't be very fresh. Under your singlet was a different story, but visible stuff was pretty closely scrutinized.