Aren’t there two large planet-like objects beyond Pluto: Quaoar and Sedna? They are both larger than Pluto and much further out.
Eris is the largest-known object beyond Pluto, with a diameter of 1850 miles, making it about two-thirds the diameter of Mercury, the smallest of the original 8. Eris takes 560 years for one revolution around the sun. Right now it is back to where it was about the year 1455...18 years before Copernicus was born.