Just binged this. Took a day, it's painful to have caught up so fast. I love this too. It feels like what the gamer could've been. Feels like a good mix between Harcore leveling warrior and The Gamer.
Anyway, Sung got strong really fast. The scale of enemies we know of that would trouble him right now are almost non-existent. Seems only the nation-levels would be tough for him. Well, excluding the system's special quests (but even those are far-fetched now). He could've taken the S-class Raid alone. Would have been difficult, but clearly the ants were fodder for his army. The 'King' and Queen at the same time might have been tough, but I'm sure he could've easily baited the King out, taken care of him then returned to wipe out the queen. It's interesting that the S-ranks are so weak though. Beru was literally stomping them easily. Btw, it would have been nice for Sung to extract Goto's soul. He was clearly a very powerful S-rank. His soul would be have been a massive addition.