Earlier quoted context omitted.
Heatwaves are a serious issue already, try being one of the few hundred million people in South Asia/SEA with 3k annual income and no aircon during April 2024. School cancelled and outdoors work nearly impossible due to wet bulb temperatures nearing the threshold of human survivability.
I meant serious as in "this place is no longer habitable".
As we go from 2C to 4C warming that's when the mass deaths near the equator should start happening from the wet bulb temperatures due to sheer lack of AC in poor areas and households. But even then we might figure out logistics and information systems to get rural and poor people to the nearest mall when a heatwave is expected, which will be often. Assuming a blackout doesn't happen. They might not die if these systems work properly, but it'll be terrible for their economy and human development indices.
At 6C warming, it's just an even worse version of the above.
Whatever the case it's going to massively suck and the people who will pay the biggest price will be the people who have pumped the least amount of carbon into the atmosphere. Life is just structurally unfair.