How do you say better in Japanese?
— もっといい (motto ii); より良い (yoriyoi)

Related synonyms for better in Japanese
break割れる (wareru), 散らばる (chirabaru)
Generic synonyms for better in Japanese
change変化 (へんか, henka); 変更 (へんこう, henkō)
good善 (ぜん, zen)
Specialized synonyms for better in Japanese
doctor博士 (はくし, hakushi, はかせ hakase)
help助けて (tasukete!)