Look at the close up of the Knight of One's face. See how the eye he has closed has two small, but obviously noticeable vertical lines intersecting with the line that makes up his closed eye? Either he has really messed up wrinkles, or that's a scar.
The Knight of One is one eyed, it's nothing new in character design. There was going to be a cyclops character eventually. Spend less time in front of the computer, it's ruining your eyesight.