Adverb from kakos (G2556, bad, evil, wicked). Kakōs means badly, in a harmful or wrong way, wrongly, evilly, wretchedly. Used to describe physical illness ('those who were ill' — kakōs echontas), moral wrongdoing, and incorrect speech or behavior.
The adverb kakōs bridges two theological domains in the NT: physical suffering and moral failure. In the Gospels, 'those suffering badly' (kakōs echontas) are the physically sick whom Jesus heals (Matt. 4:24; Mark 1:34; Luke 7:2) — his healings are visible demonstrations that the kingdom of God reverses the effects of the fall. In John 18:23, when Jesus is struck by the officer, He responds: 'If I spoke wrongly (kakōs), testify to the wrong (kakon). But if I spoke rightly (kalōs), why did you strike me?' — a calm, dignified challenge contrasting kakōs with kalōs (rightly). James 4:3 identifies a root of unanswered prayer: 'When you ask, you do not receive, because you ask with wrong motives (kakōs) that you may spend what you get on your pleasures.' The antidote to kakōs is not merely doing kalōs (rightly) but praying rightly — with motives aligned with God's kingdom purposes.