This hole in a concrete porch needs fixing
Knowing that the earth has subsided from underneath the porch (and it's all cracked, anyway), I'd ask for a discount along the lines of what it would cost to bust it up, throw it away and re-pour it.

I bet I could sink that porch into the basement with a hammer. Move on to the next house, unless you both want to play the discount game.

If you're going to call out a truck to pour 12+ yards of concrete, you might as well have a nice, entirely new pour. If we really want to get into how to 'fix' this, we'd need a lot more pictures and knowledge of the substrate in this particular situation.