To discover and prioritize landing pages for potential improvements to the user design, you should check the:
Landing Pages Report focusing on Bounce Rate metric
All Pages Report focusing on Average Time on Page metric
All Pages Report focusing on Unique Page Views metric
Exit Pages Report focusing on Page Views metric
Prioritize landing pages for UX improvements: By looking at the Bounce Rate (the percentage of single-page sessions i.e. sessions in which the person left your site from the entrance page without interacting with the page) you can see how relevant or engaging your site is to users. If you have a high bounce rate for some of your entrance (or landing) pages, you consider redesigning and optimizing them so they correlate better with the search terms that bring users to your site, with ads you’re running, or with keywords you’ve purchased.