Venus has a very slow retrograde spin (Uranus and Pluto spin retrograde), 243 days. My spreadsheet calculations for a 4 day rotation period showed 1.1E-1 km/s or as this report stated "To shed light on this mystery, scientists analyzed data from the Japanese space probe Akatsuki, which has orbited Venus since 2015. They focused on super-rotation in the cloud layer of Venus, where the rotation speed is highest, reaching about 245 mph (395 km/h) in the region surrounding the equator."
I feel good about my spreadsheet
Another link, How waves and turbulence maintain the super-rotation of Venus’ atmosphere,
https://science.sciencemag.org/content/368/6489/405, "Explaining super-rotation on Venus The solid surface of Venus rotates very slowly, once every 243 days, but its thick atmosphere circles the planet in just 4 days. This phenomenon, known as super-rotation, requires a continuous input of angular momentum, from an unknown source, to overcome friction with the surface. Horinouchi et al. mapped the planet's winds using ultraviolet observations of Venus' clouds from the orbiting Akatsuki spacecraft (see the Perspective by Lebonnois). They incorporated these data into a global model of angular momentum transport in the atmosphere, finding that the super-rotation is maintained through thermal tides driven by solar heating."
This study has applications for tidally locked exoplanets too. The slow, retrograde spin of Venus is always fun to compare with Earth - Moon system, the angular momentum differences observed---Rod
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