Light - lighter - the lightest
full - fuller - the fullest
quick - quicker - the quickest
slender - slenderer (more slenderer) - the slenderest (the most slenderer)
flat - flatter - the flattest
mad - madder - the maddest
fit - fitter - the fittest
stable - stabler - the stablest
hearty - hartier - the hartiest
early - earlier - the earliest
tiny - tinier - the tiniest
angry - angrier - the angriest
sly - slyer - the slyest
lovely - lovelier (more lovely) - the loveliest (the most lovely)