СЯУ, что слово "bad" в английском не имеет родственников в других языках, и скорее всего происходит от древнеанглийского ругательства "бэдлинг", означавшего, извините, "пидарас".
"Rare before 1400, and _evil_ was more common until c. 1700 as the ordinary antithesis of good. It has no apparent relatives in other languages. It is possibly from Old English derogatory term bæddel and its diminutive bædling "effeminate man, hermaphrodite, pederast," which probably are related to bædan "to defile." " (etymonline.com)
"Rare before 1400, and _evil_ was more common until c. 1700 as the ordinary antithesis of good. It has no apparent relatives in other languages. It is possibly from Old English derogatory term bæddel and its diminutive bædling "effeminate man, hermaphrodite, pederast," which probably are related to bædan "to defile." " (etymonline.com)