From ponos (labor, pain), poneros means actively evil — not just morally defective but malicious, harmful, wicked in intent and effect. It can describe evil people, evil deeds, or — as a substantive — the Evil One, Satan himself. This is moral evil with teeth.
The Lord's Prayer petitions 'deliver us from the evil one' (tou ponerou, Matt 6:13) — which could also be rendered 'from evil.' Most scholars see a personal reference to Satan. Ephesians 6:16 calls Satan's attacks 'the flaming darts of the evil one.' Jesus calls the Pharisees an 'evil generation' seeking a sign (Matt 12:39). The contrast with agathos (good) is stark: 'out of the good treasure of the heart, the good person brings forth good; out of the evil treasure, the evil person brings forth evil' (Matt 12:35).