Some gases don't cause any warming at all. Helium for example is not a greenhouse gas. What you looked at probably ignored those, we generally only compare problematic ones that contribute to the greenhouse effect. CO2 has been chosen as the standard to compare everything else to, I'm not sure if there's any molecule that does cause some warming but has a lower 100-year potential than CO2. Interesting question, couldn't find an answer on the quick.

There are some zero or negative GWP gases actually, like water vapor which hovers around the zero point plus or minus epsilon, HFE 365mcf3 which is below 1, and obviously argon and nitrogen are at zero. Mostly people don't record GWP values that are below 1 since e.g. any common constituent of the atmosphere contributes negligibly.

It's remarkably hard to find organic compounds that are less-bad than CO2 though. It really is the very bottom of a local minimum.

Plenty. But honestly, nobody cares about them. For example, helium is near zero.

CO2 by itself is not particularly bad. We are just emitting a LOT of it.