Occasionally meaning 'one who
blights'. But
blighting is not a common activity in today's society, and the
blight is seen more as a natural force than an activity of us humans.
Nowadays blighter is an informal tag, often used to show lack of respect for the person thus referred to. It usually refers to a male.
Can be used as a synonym either for fellow or fool.
Much more common in the UK than in America.