Click the big blue button in the top-right corner of the page and select Edit profile.
Click on the link Delete account in the window that opens.
Caution: When deleting your TeamViewer account, your entire account - including all the data it contains - will be permanently deleted. This includes all of the groups you own and the computers and contacts inside them. This data cannot be recovered later!
Note: If your account belongs to a TeamViewer company profile, the link Delete account is not shown. In this case, you do not have permission to delete your account as you are a part of a company profile. You will need to contact the administrator of your TeamViewer company profile and ask them to remove your account for the company profile. Afterwards, you can see the Delete account link again.