But causing the nuclear dismantlement to be delayed by five years is not the hallmark of a good president; it's a hallmark of GW Bush. He could have actually sped up the process by pressing North Korea in early 2002, just after the US ousted the Taliban and put the whole world in awe. He could have also done something about Iran's nuclear program back then, but he lacked the vision to exploit one of the the biggest diplomatic opportunities in history.
And let's not ignore North Korea's nuclear bomb failure, which certainly could not have encouraged them to continue their defiance.