The leader is very unpopular, his approval rating is currently 20% approval, 71% disapproval according to Morning Consult, reaching lows of 18% approval, 75% disapproval.
Also there have been strikes against neoliberalism, US robbing the country, anti-war protests and getting the president to resign. Ryomyong.com covers resistance to him. http://ryomyong.com/index.php?page=south
As for a SK communist party, there's http://pdp21.kr/ but it's small, there's also Anti-Imperialist National Democratic Front which is an underground DPRK org in SK.
It signs solidnet.org statements.