Comparative:

1.more expensive

2.thicker

3.friendlier

4.finer

5.thinner

6.more difficult

7.warmer

8.wiser

9.easier

10.more wonderful

11.sunnier

12.fatter

13.longer

superlative

1.the most expensive 

2.the thickest

3.the friendlest

4.the finest

5.the thinnest

6.the most difficult

7.the warmest 

8.the most wisest

9.the easiest

10.the most wondelful

11.the most sunniest

12.the fattest

13.the longest

expensive -> more expensive -> the most expensive

thick -> thicker -> thickest

friendly -> more friendly -> the most friendly

fine -> finer -> finest

thin -> thinner -> thinnest

difficult -> more difficult -> the most difficult

warm -> warmer -> warmest 

wise -> wiser -> wisest

easy -> easier -> easiest

wonderful -> more wonderful -> the most wonderful

sunny -> more sunny -> the most sunny

fat -> fatter -> fattest

long -> longer -> longest