After 60+ hours of research & testing, we’re comfortable recommending the RMR-86 Instant Mold & Mildew Stain Remover as the best mold killer for your dollar due to its’ effectiveness, versatility and ease of use. It’s a bit smelly and it’s not one of the cheaper options ($17 versus lower quality options in the $9-12 range), but if you want the BEST, this is it.