Simple Keynesian model of income determination When determining equilibrium, we take consumption equal to C= ¢ + c' y where ¢ is the autonomous consumption or minimum consumption that would take place even in absence of income.
What could be the consequences on equilibrium income if the autonomous consumption ¢ was negative?
I cannot see any way to have negative autonomous consumption. I believe autonomous consumption's extreme is zero if there's a kind of superheroes who don't need water, electricity and food to live and they save everything they earn. But in a case like this, there's  no reason for having aggregate supply at all as nobody will buy the goods in first place.