that's enough!; cut it out!; get a life!
A strong, blunt imperative telling someone to stop their unreasonable or annoying behavior. Often used in anger or exasperation. The softer form いい加減にしなさい is more common in parenting or less harsh situations.
See also: いい加減にしなさい
That's enough already! How long are you going to keep complaining?
Cut it out, lying like that all the time.
いい加減にしろ is a blunt, angry command to stop, while いい加減にしなさい uses the softer なさい form typical of a parent scolding a child.
From いい加減 (moderate, reasonable) + に + する (to do) in the imperative form しろ, literally 'make it reasonable', used idiomatically to tell someone to stop excess.