It is better to say...
Remember the rules for forming comparative adjectives.
1 For short adjectives, add -er: tall - taller, big - bigger, cool - cooler, pretty - prettier, easy - easier
2 For long adjectives, add more: more beautiful, more expensive, more important, more difficult
3 BUT for 'good' and 'bad' do NOT follow rules 1 and 2.
good - better
bad - worse