I have a little problem with Illustrator CS6. Like the title says, when I intersect two shapes, remains a line between them. How can I fix this problem, because I don't want to use another option from the Pathfinder panel.
extend the lines of the 'K' to beyond the boundaries of the circle before intersecting.
this issue is caused because the boundaries of each shape are on top of each other but not quite identical (it would appear the 'K' is fractionally smaller than the circle)
when subtracting from above it's often worth leaving overhang to avoid situations like this :)
So here's how you go about this:
Select both circle and outlined K
Open Pathfinder (Window > Pathfinder) and select 'Minus Front'