Crowded
more crowded / the most crowded
Hot
hotter / the hottest
Attractive
more attractive / the most attractive
beautiful
more beautiful / the most beautiful
Heavy
heavier / the haviest
Slowly
more slowly / the most slowly
Tall
taller / the tallest
Strong
stronger / the strongest
Carefully
more carefully / the most carefully
Interesting
more interesting / the most interesting
Nice
nicer / the nicest
Clean
cleaner / the cleanest
Soft
softer / the softest
Good
better / the best
Ugly
uglier / the ugliest
Fast
faster / the fastest
Big
big / the biggest
Slow
slower / the slowest
Bad
worse / the worst
Long
longer / the longest
Old
older / the oldest
Quiet
quieter / the quietest