You have countries ignoring sanctions and embargoes because there's a lot of money to be made that way.

But you also have success stories of sanctions and embargos inflicting serious pain: just to name the ones I know of off the top of my head, Japan apparently felt itself forced into WWII by a US embargo of necessary supplies, North Korea remains a hellhole and has trouble selling stuff like it used to which forced it to come to the negotiating table over the bank embargos, and Iran is currently grappling with uncontrollable inflation (which may result in hyperinflation) which is attributed to the existing relatively mild sanctions.