発勁[hakkei] release internal power
勁捷[keishou] strong and nimble
勁卒[keisotsu] excellent soldier
勁敵[keiteki] formidable foe

勁悍[keikan] strong and fierce
雄勁[yuukei] vigorous
勁草[keisou] wind-resistant blade of grass

敵わない[kanawanai] no match for
怨敵[onteki] sworn enemy
外敵[gaiteki] foreign enemy
敵う[kanau] to come true (wish)
仇敵[kyuuteki] bitter enemy

敵討[katakiuchi] vengeance
敵同士[tekidoushi] mutual enemies
旧敵[kyuuteki] old enemy
強敵[kyouteki] formidable enemy
公敵[kouteki] public enemy