Stiff is a related term of unmitigated.
As adjectives the difference between stiff and unmitigated
is that
stiff is of an object, rigid, hard to bend, inflexible while
unmitigated is not mitigated.
As a noun stiff
is an average person, usually male, of no particular distinction, skill, or education, often a
working stiff''''' or ''lucky '''stiff .
As a verb stiff
is to fail to pay that which one owes (implicitly or explicitly) to another, especially by departing hastily.