the handful of megacorporations emitting 80% of all green house gases
That's just nonsense.
The top two providers in that list are the governments of USSR and China. They are not "megacorporations"
It not a list of "emitters". These entities are just "linked to" the emissions -- i.e. they provided the fuel that someone else burned.
It's completely ridiculous to say that it doesn't matter that someone burns 1,000 gallons of fuel a day because a big company sold it to them.
Targetting individuals people or companies is useless. There's over a billion co-contributers, not a handful. Systematic changes like a carbon tax are necessary.