Feint doesn't have accounts, and there's no server where your data lives — everything is stored locally, on your own device. That means you can already delete anything, instantly, yourself, without waiting on us. Two ways to do it, below.
Remove a single favorite, saved route, or history entry, without touching anything else.
Since nothing is stored anywhere but your own device, uninstalling either app erases all of its locally-stored data — favorites, history, saved routes, and settings — completely and immediately. There's no separate "delete my account" step, because there's no account or server-side copy to delete from.
If the app has already sent a crash report before you delete anything, that report has already left your device and is held by Google/Firebase Crashlytics under their own retention policy — uninstalling Feint afterward doesn't recall a report that was already sent. See Google's Firebase privacy policy for how they handle that data. Nothing else in this list applies — location history, favorites, and saved routes never leave your device in the first place, so there's nothing to recall for those.
See also the Feint Privacy Policy for the full picture of what data Feint handles and why.