Cleaning black mold is beating me

If it keeps coming back, the cleaning isn't the problem, the moisture is. Find out why that spot is damp first, a leak, condensation on a cold wall, no ventilation. On tiles, glass and sealed surfaces, scrub with detergent and water, dry it well. On drywall or anything porous, bleach only bleaches the surface, the growth is inside, so badly affected board usually has to be cut out and replaced. Wear an N95 and gloves either way. If it's a big area, much past a few square feet, I'd get a pro in.