Which planet has carbon dioxide in its atmosphere?

Mars, Venus, Earth, and probably all the gas giants. It remains ambiguous as to whether or not the Plutoids and Cubewanos, or any other asteroids, have gaseous carbon dioxide.

Venus and Mars have about 95% carbon dioxide in their atmospheres, but the atmosphere of Venus is very much thicker. Earth has only a small amount of carbon dioxide, but it's enough to have a "greenhouse effect". Mars may have once had a denser atmosphere, but now it is so thin that its effects are negligible.

The gas giants are simply humongous, and contain a very large number of elements and compounds, though the majority of these volumes are occupied by hydrogen and helium. Since Saturn and Jupiter are so hot (their mass generates heat), only the outermost layers contain compounds. The amounts, thus, of CO2 in the latter two planets, would be negligible by percentage, though ample by comparison to the terrestrial planets. The amounts of CO2 in the ice giants (the outer two gas giants, which are made up mostly of ices and liquids) is even less than in the proper gas giants (the four together are collective classified as Jovian Planets).