It isn't clear what potential you are talking about.
Mercury is the smallest and the least massive planet, out of the eight in our solar system.
Mercury.
Saturn is the least dense planet in our solar system.
The planet with the least mass and smallest is Mercury. The planet with the lowest density is Saturn
pluto
Mercury is the smallest planet in the Solar System
Saturn is the least dense planet in our solar system.
Complex Life. (in our solar system at least)
In our solar system it is Jupiter
All of them are - at least, the planets in the Solar System.
Neptune is our 8th planet in the solar system!
Neptune has an average temperature of -200C, making it the coldest planet in the solar system (at least now that Pluto has been demoted from planetary status).