ガチンコ
〔手加減しないこと〕ガチンコ勝負[対決]a do-or-die contest; a confrontation [face-off] one puts 「everything one has ...
ガチンコしょうぶ【ガチンコ勝負[対決]】
a do-or-die contest; a confrontation [face-off] one puts 「everything one has got [all one's might...
ガチンコしょうぶをする【ガチンコ勝負をする】
battle with ((an opponent)) 「in earnest [wholeheartedly/with everything one's got]