We can terraform Venus, it is not that difficult. Venus is extraordinarily hot, and has a very thick atmosphere. The pressure and temperature on the ground are both immense. But there's an intervention that we can perform that is close to our current technological capabilities. If we put a large sunshade in front of Venus, so we decrease the amount of light that comes from the Sun and hits Venus, then we can cool off the planet. If we cool it to -80 °C the CO2 from the atmosphere will freeze and turn into dry ice and fall and settle on the ground. The remaining part of the atmosphere will be N2, at roughly the same pressure as on Earth. The albedo from the dry ice could be enough that the solar shade might not be needed anymore.

How much would such a sun shade weight? Current solar sails weigh between 3 and 5 grams per m2, so 1g/m2 is probably possible in the near future. That is one ton per km2. The radius of Mars is 6000 km, so the area of the cross-section is about 100 million km2. To obscure a few percent of that would take a few million tons of material. That's a lot, but a million ton is the cargo capacity of 5000 Starships. It's not completely impossible.