In a best case scenario, I assume it'd start with the nations of the global south being able to resist the US and EU enough to sustain and develop their countries without having to be hyperexploited by the core nations.

Maybe a domino effect of those global south countries implementing some hybridization of state capitalism/planned economies in those regions of the world; the rest just cascades from there. I assume this might be the case due to the ecocide of the planet prompting this response where the market will inevitably fail in the face of failed crop yields, water droughts, famine, energy and medicine shortages, etc.

The west will discard liberal democracy in its interior and in its place build a fortress empire and further empower repressive internal security apparatuses to maintain control. Altered Carbon & Elysium are likely futures rather than Star Trek or even the world of Interstellar.

The worst case is that capitalism's collapse will coincide with the ecological collapse, destroying capitalism altogether and slowly regressing into a canvass of failed/failing states. It is very possible that our ruling class will choose omnicide rather than having to live with less privileges and treats.