You mention pricing externalities being important; it's also important that corporations don't have undue influence in their own regulation, or externalities will become chronically underpriced.
I also think "just profitability" isn't quite correct. Profitability is sometimes antithetical to efficiency and sustainability; take artifical scarcity or planned premature obsolescence, for example.
[On that topic: I've wondered before whether corporations are darwinian. They are large, amoral machines that have a life their own, and presumably the corporations that survive (and that are around today) are the corporations that act in the interest of their own self-preservation, not in the interests of people or life on earth. I have no idea whether the time scales involved are sufficient for the evolution of corporate strategy, but it's fun armchair philosophy.]
Fortunately, "markets" is not synonymous with "capitalism" – markets feature in many economic systems, so we have options.