mad
madder
far
further/farther
poor
poorer
friendly
friendlier
sad
sadder
icy
icier
clumsy
clumsier
young
younger
long
longer
large
larger
good
better
happy
happier
soft
softer
nasty
nastier
silly
sillier
thin
thinner
easy
easier
creepy
creepier
healthy
healthier
angry
angrier
busy
busier
slim
slimmer
bad
worse