Some translations for the expression いいかげんにしろ！ are:
that's enough!; cut it out!; get a life!
If the correct kanji of this expression is 好い加減, what is the literal meaning of both 好い and 加減 in this expression?
いい加減 can also be used with a negative connotation with the meaning "sloppy" (almost opposite of the original meaning) as in the sentence given in yadokari's comment to this question. As for why, that may be a good independent question; there are some other words like that.