Hello Edmond.
There are many tools for SEO, each useful and valuable in its own place. So it is impossible to say which is the best tool. For example:
- Google Search Console [+]
- Google Analytics [+]
- Clearscope [+]
- Semrush [+]
- Ahrefs [+]
- Moz [+]
- Surfer SEO [+]
- SE Ranking [+]
- WooRank [+]
However, keep in mind that the above list is only some of the best tools for SEO. To get more information, you can increase the scope of your research and questioning.