Please note, if you are simply trying to avoid payment, you can cancel your subscriptions and leave your account inactive here: splice.com/profile/plans
If you wish to permanently delete your account, you can do so here: https://splice.com/profile/settings
Navigate to the bottom of the page, and you will see "Delete Account" highlighted in red.
Click on that and you can delete your account after entering your username.
Please be aware that all of your likes, collections, samples, and plugins will be deleted as well. Before deleting your account, you should ensure all of your Sounds are downloaded to your local drive. You can find more info on downloading all of your Sounds and presets here: https://support.splice.com/en/articles/8652661-how-do-i-download-all-of-my-samples-and-presets-at-once