To completely delete all your portfolio data, simply delete all your portfolios.
To do so:
Tap the hamburger icon (top-left) or swipe from the left edge on the portfolio screen to bring up the 'Portfolios' menu.
Once the portfolios menu is open - tap the hamburger icon with a pen in it, directly to the right of the "MY PORTFOLIOS" heading.
Then on the red delete icon (red circle with white dash) to completely remove a portfolio. The app will ask for your confirmation before deleting.
Please note that this action is irreversible! The portfolio cannot be recovered EVEN IF you have a recovery code because the recovery code is dynamic and it is not a snapshot.