• 勁敵けいてき

  formidable foe

• 勁悍けいかん

  strong and fierce

• 勁捷けいしょう

  strong and nimble

• 勁草けいそう

  wind-resistant blade of grass, resistant idea (metaphorically)

• 発勁はっけい

  fa jin, releasing internal power explosively

• 雄勁ゆうけい

  vigorous, powerful

• 簡勁かんけい

  crisp, curt, laconic, terse, spare