Hungry - hungrier - the hungriest
Difficult - more difficult - the most difficult
Big - bigger - the biggest
Dark - darker - the darkest
Yellow - yellower или more yellow (зависит от подтекста) - the yellowest или the most yellow (тоже зависит от подтекста)
Young - younger - the youngest
Old - older - the oldest
Long - longer - the longest
Foggy - foggier - the foggiest (точно не знаю)
Tall - taller - the tallest