Kaneki was on RC suppressants for a long while until quite recently and he's become able to control how his Kagune forms since he made that creepy one with all the mouths and hands. I think at Kaneki's current state he's strong enough to defeat Spider Man
Great topic! There are definitely going to be some tough creatures to meet and Nen certainly exists in the dark continent because we know Nanika is from there (which i really really hope we learn more about). Even though Chimera Ants have been assessed as a far lesser threat than they clearly were in the CA arc, their humanity was a huge disadvantage to their order and definite need to kill. It's possible there'll be creatures more like Mike who are unfeeling and terrifying so maybe there are still stronger foes out there.
At the same time I agree with many people that the main threats will likely be a battle of conditions and against diseases. Throwing in a plot about the princes having a battle for the throne and we can already see there'll be a lot of deceit or alliances having to be made to survive the conditions. Super exciting prospect!
I admire Togashi so much for continuing work on this, the DC arc has a lot of potential