Every display I've seen seems to be correct with the Sharpness at the factory setting, which is usually 50%. Be careful about setting it to zero -- that's not 0 increase of sharpness, that's zero on a scale from zero that's lack of detail to 100 that's ringing and noisy.

My simple amateur setup for TVs is this:
Turn off all the fancy picture features, as recommended.
Set color all the way down. You'll run into some TVs that have color all the way down until that last click, but turn it off.

Set sharpness to middle. Set tint to middle.
Turn down Contrast (or Picture, same thing) until you do not see actual white in the picture. View several sources, especially live news. Don't rely on live camera shots in the field for this - use studio shots.
Turn up Contrast until you have a WHITE in the picture.
Turn Brightness (which is, ironically, black level) until the image has no blacks, only 50 shades of Grey... then turn it all the way down until you cannot distinguish adjacent dark areas from one another. Now that you've seen both extremes, adjust Brightness so that you can see details in the black, but there still is black. You should be able to distinguish the lapel and the main cloth section of a tuxedo jacket. Again, look at different examples of video.

Now you have a decent black and white picture. Turn up the color. Watch skin tones. Red or purple people are just wrong! Black people have skin tones that challenge TV systems, so you can do some further fine tuning with their faces.

Be aware that you might not be able to adjust the TV properly. I set up some Samsung RPTVs a few years ago where proper adjustment of black level for a dark scene resulted in a scene that went, from top to bottom, as sky, mountains, shadow of mountains, where almost all of the mountain shadow was almost solid black. Adjusting for that picture, the dark scene had various shades of gray. You might have to realize that you can adjust the TV to prove that it's a piece of crap!

Best of luck.