I think the first question is a little controversial, considering the uncertainties when saying HOW bad it is gonna be and considering that implications of climate change vary so much around the planet, e.g. in some areas people might actually experience benefits from a warming climate, e.g. prolonged growing season.
But for me, the worst case scenario is simply people whose life and livelihood is in danger (which seems to be already reality, though it is rare that certain events can be clearly linked to climate change). Have a look at the article I linked to. It suggests that it might have been climate change that partly caused droughts in the Middle East and consequently the war in Syria. And I imagine this could be a glimpse of what the future could look like. In some areas livestock will perish, food and water (!) prices will rise and people get sick, sparking conflicts and causing large scale migration that eventually also affects people that might not care about climate change, thinking they don't have to worry about its consequences.