Spam attack and Website Indexing

I have set up an SEO campaign for my website and enabled indexing for crawling. However, the website experienced a Japanese spam attack, resulting in numerous spam posts being published and indexed. We have removed almost all the spam posts from the backend, but the website's indexing has been affected. Even for brand keywords, the website is not appearing on the first page of Google SERP. It has been more than seven months with no improvement in the website's indexing. Can anyone analyze this issue and let me know how long it typically takes for Google to properly reindex the website?