To measure success as an SEO analyst, the individual has to declare the KPIs (Key Performance Indicators) at first. The KPIs may include social media shares, organic traffic, impressions and number of visitors, to increase the brand awareness and many more depending upon the benefits of the SEO.
The regular and growing analysis of these KPIs with time shows the success of the website's SEO. For this, an SEO analyst will need various paid tools other than Google Analytics.