Here are some expressions including oni.
Oni ni kanabou 鬼に金棒
(Literally means, "Oni with an iron club")
--To make one invincible.
Oni no inuma ni sentaku鬼のいぬまに洗濯
(Literally means, "Do laundry while oni are away")
--When the cat's away, the mice will play.
Oni no kubi o totta you鬼の首を取ったよう
(Literally means, "As in beheading oni")
--To achieve a major success.
Oni no me nimo namida鬼の目にも涙
(Literally means, "A tear even in an oni's eye")
--Even the hardest heart will sometimes be moved to pity.
Kokoro o oni ni suru心を鬼にする
(Literally means, "To make one's heart an oni's")
--Harden one's heart against pity.