How do you say much in Japanese?
— 沢山 (たくさん, takusan); 多く (おおくの, ōkuno); 多い (おおい, ōi)

Related synonyms for much in Japanese
oftenよく (yoku); 度々 (たびたび, tabitabi); 頻繁 (ひんぱんに, hinpan-ni); しばしば (shibashiba)
Antonyms for much in Japanese
little小さい (ちいさい, chiisai)