You can remove the Klarna payment method in Shopify store settings.
To remove Klarna from your Shopify checkout, deactivate the alternative payment method in Shopify admin > Settings > Payments.
After deactivating a payment method, you’re given the option to remove the corresponding payments app, but we don’t recommend removing the app until all Klarna orders have been finalized. The app supports order management updates, for example refunds, from Shopify to Klarna.