How do I delete this account totally.. made by mistake

Hopefully, you don't have a credit card on file, because they will likely charge it, then make it harder than hell to get your money back.  

• Sign in as an Admin to your QuickBooks Online account
• Select the Gear icon in the top right corner
• Choose Account and Settings
• Click Billing and Subscription
• In the QuickBooks section, select Cancel
• Select Continue to Cancel, then Continue to Cancel again
• Finally, answer the exit survey questions - this feedback helps us make our Product better
• Then scroll down and select Confirm Cancel

You are able to resubscribe to the same account within 12 months of the day you

Welcome to the Community.

I'll help you cancel your subscription since the account was created by mistake.

The steps to cancel your subscription depend on where you signed up.

Follow the steps below to cancel an account purchased online directly from Intuit.

1. Sign in to the Intuit Account Manager.
2. Choose Products & billing, then select your company name. This will take you to your subscription page.
3. Find the product you wish to cancel, then select Cancel.
4. You’ll see a multiple-choice survey on why you're canceling your subscription. Once you’ve filled it out, click Continue to cancel.
5. When you see a page that details product benefits and the last day you'll be able to use your subscription, select Continue to cancel.
6. You’ll see a pop-up confirming your subscription is canceled. Click Got it.

For the detailed steps to cancel your subscription purchased the other way, like the Apple App Store or Google Play Store, refer to the bottom of this article: Cancel your QuickBooks Online subscription or trial.

If you are within the billing period you last paid, you can continue your subscription and maintain the same billing cycle by choosing Resume subscription.

For future reference, you can read this article about resubscribing if you decide to continue using your account after the cancellation: Resubscribe to or reactivate QuickBooks Online.

Don't hesitate to comment below if you need further assistance canceling your account. I'm always here to help. Have a great day.