Terraforming Venus presents numerous engineering challenges, but none that are theoretically insurmountable. The heat, continuous acid rain and crushing pressure of the Venusian atmosphere is almost entirely the result of excess carbon dioxide in the air. Removing it solves many of the main problems in making Venus habitable.
Scrubbing CO2 from Venus' atmosphere can be done by shading the planet from orbit. Once the temperature drops below -78.5 degrees Celsius, the CO2 can precipitate out as snow that can then be collected and buried. Final conversion of the air can then be done by bacteria and plants. Nothing can be done about the planet's 116-Earth-day solar cycle, but the same orbital shades that cooled the planet, combined with orbital mirrors, could theoretically provide an Earth-like climate.