Venus doesn't have magnetic field. Because of it, Venus lost hydrogen from its atmosphere due to solar wind. Because of it Venus became very dry. So, it had not life and ways to fix CO2 in carbonates in water. It resulted in large accumulation of CO2 in atmosphere and strong greenhouse effect. It changed the way its mantle creates continents as dry mantle is not plastic. There is no plate tectonics on Venus. The surface changes every half a billion years in one large "supervolcanic" event.
There is also the little issue of Venus receiving about twice the insolation than Earth....
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