Evil

up to no good

Meaning: to have an evil plan

Example: The children can be up to no good cooped up in that attic together for two hours. You must go up and check. Read on

necessary evil

Meaning: something unpleasant that must be done in order to achieve a goal or objective

Example: Mike saw his going to work for his father as a necessary evil if he was ever to own his own company someday Read on