Runkeeper is in my personal opinion the best app for runners and cyclists, I’m using it myself too. But if you want to remove a Runkeeper account, you can easily do that in the Settings of your account.
I’ll show you below how I managed to close my profile using a desktop computer:
1 Go to http://www.runkeeper.com and log in to your account
2 Click on the gear icon and choose Account Settings
3 Select Promotions and Privacy in the left menu
4 Delete your account
is a link that you’ll find on the bottom of the page (it’s in Privacy and terms of service)
5 Confirm that you’re sure that you want to close you’re account
and that you’re aware of the fact that all your data will be lost.
6 Last step before closure
is that you enter your password, indicate a reason for removal and that you’re not a robot.
You’re now good to go.
Your profile has been removed and you’ll be redirected automatically to the homepage.
Source screenshots (& thanks to): Runkeeper desktop website