What is the worst spider to be bitten by?

Brown recluse?: Some would say the brown recluse spider, because the wound can ulcerate for many weeks afterwards. The venom contains enzymes that destroy tissues; also it induces an immune response marked by swelling and inflammation. The initial bite is usually painless, but is followed in a few hours by burning, pain, and itching. Surgery may be needed to debride the dead tissue.

Depends: This will depend on what part of the world you are bitten and by what species. In order from worst to less (1 to 10): brazilian wandering spider, african six eyed sand spider, sydney funnel web, black widow, aussie reback spider, brown and chilean recluse, aussie mouse spider, fringed ornamental tarantula, yellow sac spider.