QNED: less strong contrast
QNED televisions use backlight with dimmable zones or pixels. TVs with dimmable zones have a less strong contrast, because this way of dimming is less accurate. Some QNED TVs use Mini-LED backlight. The pixels dim themselves individually with this, which provides better black levels and a good contrast. A QNED screen does have a less strong contrast than an OLED screen. This is because a QNED screen can't completely turn off the pixels, so the TV doesn't show true black.
OLED: strongest contrast
With an LG OLED television, you can be sure of the strongest contrast with the deepest black levels. With the millions of individually dimmable pixels of an OLED TV, pixels can turn themselves off completely. This way, black images are really black. You can see that with images of a starry sky, for example. The sky is really black, while the stars jump out brightly. You also don't see a glow around the lights with LG OLED television, because the pixels around the lights turn themselves off completely.