In the English Grammar Profile, A2 point 13 in the category of ADJECTIVES/superlatives:
one syllable with a short vowel, by doubling the final consonant and adding ‘est’
PELIC STUDENT EXAMPLE:
Consequently, Darwin’s theory on survival of the fittest no longer applies to humans.
Survival of the fittest mainly relies on nature or predators to eliminate the young, old, weak or unfit,
yet humans today no longer fear animal attacks or blizzards.
Chinese level 5 writing class.
Here are the superlatives we found in a search in iWeb corpus for:
_JJT
4 BIGGEST 1122195
How does it feel to be the biggest hero in Gotham?
25 HOTTEST 102428
83 FITTEST 10804
90 SADDEST 9545
113 WETTEST 6532
157 FATTEST 2870
167 SLIMMEST 2726
170 HIPPEST 2625
183 FUNNEST 2376
207 FLATTEST 1785
329 DIMMEST 839
363 MADDEST 658
414 RADDEST 490
428 GRIMMEST 463