Something avoidable can be averted or dodged. Death is not avoidable.
When you can avoid something, there's a way around it. A fast quarterback can avoid a linebacker blitzing, and daily exercise is a way to avoid gaining weight. Anything that can be avoided is avoidable. Late fees are avoidable if you pay your bills on time. The flu is avoidable if you get a flu shot. An annoying neighbor is avoidable if you get in your apartment before he spots you. Whew!