Best On Page SEO Tools
CORA - Maybe the most power SEO tool there is today. This tools analyses 600+ different potential ranking factors for the top 100 keyword for a specific 'keyword' and correlates which factors have an effect on rankings.
Page Optimizer Pro - This tool analyses many scientifically tested and verified ranking factors for a specific keyword against the top competitors you manually select. The tool then provides guidance as to what factors you should change in order to beat the competition for that specific keyword.
Best Off Page SEO Tools
This tool does it all, keyword research, backlink checker, broken links, site audits, rank tracking. This is one powerful SEO Tool.