不知利害

see 不知好歹[bu4 zhi1 hao3 dai3]

no; not so / (bound form) not; un-

not to know / unaware / unknowingly / fig. not to admit (defeat, hardships, tiredness etc)

to know / to be aware

sharp / favorable / advantage / benefit / profit / interest / to do good to / to benefit

pros and cons / advantages and disadvantages / gains and losses

terrible / formidable / serious / devastating / tough / capable / sharp / severe / fierce

to do harm to / to cause trouble to / harm / evil / calamity