I am looking for the most complete theme..
No such thing all business needs are different "complete" is as arbitrary as a "theme that has everything".
It's often code for lack of definition of feature requirements really only solved by sitting down and doing something like feature discovery or competitor analysis.
include templates for account registration, login page, my account page, etc.
Those are required parts for all shopify themes to have as basic templates for the theme store(all themes with filter options),.
So not indicative of "completeness".
What helps is listing your industry, website samples, expected features: examples: notifications,email subscription, ajax cart, large images, etc etc
And also listing out any issues with the current theme, if you recently bought it from shopify probably asking support for a trade in.