The highest display resolution of the Panasonic TX-50AX802 is 4K Ultra HD. That's over four times the display resolution of the most common HD type of Full HD. 4K Ultra HD TVs have a resolution of 3840 x 2160 pixels.
A 4K Ultra HD HD type is actually the best display resolution across all televisions of a comparable type and age to the TX-50AX802.
The worst display resolution amongst comparable types of TV is Full HD.
4K Ultra HD TVs have a resolution of 3840 x 2160 pixels.
Alternative 4K Ultra HD televisions currently available which you might want to look at include because of it's better review score, the LG 55UB820.