How do you say wimp in Japanese?

Answer 1

弱虫　よわむし　yowamushi

臆病者 おくびょうもの okubyoumono

腰抜け こしぬけ koshinuke

卑怯者 ひきょうもの hikyoumono

yowamushi is the weakest form, kind of like calling someone a scaredy cat. Usually used by or directed to children.

koshinuke is disparaging and is probably the most appropriate translation of wimp.

okubyoumono is also disparaging, but not as curt as koshinuke.

hikyoumono would be rarely used and basically refers to someone who uses under-handed tactics to gain an advantage; i.e. a cheater and coward. It's used a lot in action manga and anime.