Complex words contain whether a bound and a free morpheme (eg unhappy) or two bound morphemes (eg intervene). In the first case (eg unhappy) the complex word is polymorphemic because it includes a free,lexical morpheme (eg "happy"). But when the complex word consists of bound morphemes, is it polymorhemic?
I presume you are talking about Complex vs Compound words.
A complex word consists of a stem and an affix which the affix does not have any meanings alone.
A compound word on the other hand has an affix which has a meaning standing alone.
Poly-morphemic, as the name suggests, is a word which has either a suffix or prefix. and yes all the complex words are polymorphemic