Earth, Mercury, Venus and Mars, which of these planets is the least suitable for human habitation?

Venus is not suitable. If humans choose to send people to explore these planets in the future, it is absolutely impossible for Venus to visit people first, and the air pressure is 90 times that of the earth! It is equivalent to the pressure of 900 meters deep in Shanghai! Then the global temperature is extremely high, nearly 500 degrees high temperature! There may be hundreds of thousands of volcanoes erupting around the world, and the proportion of carbon dioxide is very high. High temperature will melt lead and tin! Turn into a liquid lake! The atmosphere is a cloud of sulfuric acid, and that place is hell!

Although Mercury is close to the sun, its rotation is slow. It is no problem for humans to go to the dark side of Mercury, but the surface temperature irradiated by the sun is also close to 500 degrees!

Mars is certainly the best planet to land on! The temperature is suitable, there is a certain atmosphere, and the surface is very similar to the earth.

To sum up, Venus is of course the least suitable.