Venus

Venus is Terra's evil twin, the deadly and hellish to the Earth's (relative) peace and tranquility. Unless you're in Sci-Fi, in which case we conquered the planet and terraformed it into Earth 2.0 or better.

Overview

Venus, being the brightest object in the night sky that isn't Luna, has likely been seen in the night sky since the days man was not too far off from animal (i.e. still primitive hunter gatherers).

Venus is the 3rd planet from the Sun and is notable for being similar to Earth in size. However, that's where the similarities end - with a ridiculously thick carbon dioxide atmosphere both crushing you and causing the planet to be fuck-off hot, standing on Venus in the present day is for all intents and purposes instantly deadly. There's a reason why it needs to be terraformed in Sci-Fi stories, after all.