I Was playing space engine and i was looking for a planet like Earth for quite some time and then i stumbled on this beautiful world covered with liquid water which orbited a main sequence star with 8 other planets that ticked most of the boxes for human survival, with a small plot of land. This planet is 77% Earths diameter, 0.47 times Earth's mass, 0.78 G surface gravity, and its Rotational period is 2.3 earth days about (55 hours long) and its orbital period is about (766 Earth days) in total, and its temperature ranges from 25-38 centigrade. Even with these close similarities it was the atmospheric composition which caught my eye, its atmospheric pressure is 0.5atm (Half of the earths surface pressure) and its atmospheric composition consists of: N2 = 40.5% CO2 = 31.4% O2 = 26.4% H2O = 1.5% SO2 = 0.136% CH4 = 955 ppm C2H6 = 75.5 ppm
31.4% CO2 is way too high. According to Wikipedia, you can last about 0.1 hours in 7% CO2, and that's even when there's otherwise enough oxygen in the air. I think plants would be able to survive it, so if you seed the planet with enough plant life you could bring down the CO2 levels to make it habitable within a century or two.
The SO2 levels are also way too high, and I'm not sure how you'd take care of those. Based on the Wikipedia page for SO2, a safe level is 75 parts per billion (0.0000075% instead of your 0.136%). "Sulfur dioxide emissions are a precursor to acid rain", so this also makes it harder for plants to grow, making it harder for you to get rid of the CO2.