Comparative: more northern Superlative: most northern
We usually use more northern for the comparative and northernmost for the superlative. Ordinarily, you'd expect northerner for the comparative of northern, but there is a very common noun northerner, which may be why the Frenchified "more northern" is the usual form. Again, you'd expect northerrnest as the comparative, but with directions, such as northern and southern, top and bottom, upper and outer and so forth, the superlative is usually formed by adding -most: northernmost, uppermost etc.
"Litter" is a noun and a verb and, as such, does not have a comparative degree.
smoother is comparative of word smooth.
A comparative for the word ineffectual is more ineffectual.
The comparative is hotter.
comparative
Sharper is the comparative form of the word sharp.
comparative
comparative
Worse is the comparative word.
The comparative form of the word 'fast' is 'faster'.