Can you activate the whole pixel on LCD?
The LCD is made up from 32 characters each is 5x7 pixels in size, with a 1 pixel gap between each character.

You can never put anything in the gap between the characters, as there is just nothing there.

But what you can do is define your own characters to fit within the 5x7 pixel rectangles.

Some variants of the HD44780 have character 255 as a solid block, but not all (it depends on what language the ROM is).  If you have one that has that character you can just print it with lcd.print("\xff") or lcd.write(255).  If it doesn't it will print ÿ instead. In that case you will have to define your own character.

One benefit of defining your own characters is that you could then do partial blocks to give you a higher resolution.  Here's an example:



You can find that example and the code that goes with it here.