Itchier is the comparative form and itchiest is the superlative form.
Comparative: My new shoes are itchier than my old shoes.
Superlative: Those cheap shoes you can get at the local department stores are the itchiest shoes I've ever tried.
The comparative and superlativeforms of grand are: Comparative: grander Superlative: grandest
Comparative: shallower Superlative: shallowest
The comparative is "stricter" and the superlative is "strictest".
comparative = sadder superlative = saddest
The comparative is grumpier and the superlative is grumpiest.
comparative : purer superlative : purest
Comparative: older Superlative: oldest
Dative; Early Comparative; Earlier Superlative; Earliest
The comparative and superlativeforms of grand are: Comparative: grander Superlative: grandest
comparative - merrier superlative - merriest
comparative = sadder superlative = saddest
The comparative is "stricter" and the superlative is "strictest".
Comparative: shallower Superlative: shallowest
The comparative is greater and the superlative is greatest.
Comparative: Whiter Superlative: Whitest
Comparative: unrulier Superlative: unruliest
Luckier, luckiest. Luckily doesn't have comparative and superlative forms but the comparative and superlative of lucky are as above.