He's such a coward that he can't even complain.
With that spineless attitude, nothing will change.
意気地なし means 'spineless person, coward' with emphasis on lacking backbone or resolve, while 臆病者 emphasizes fearfulness itself.
意気地なし is a stronger, more contemptuous put-down for lacking willpower or backbone, whereas 弱虫 is often used lightly in teasing.
Standard kanji-kana mixed spelling.
Variant spelling using the kanji 無 for なし.
Compound of 意気地 (いくじ, 'spirit, courage') and なし ('without'). The exact historical derivation is uncertain, but the word has been used since the Edo period to describe a person lacking backbone.