Deleting athletes can be done from the Cloud's Team Management. 

From the top left corner, select Menu and then Team management.

Next click Add existing athletes button from the bottom of the page. You don't have to have that team open where the athlete profile you are deleting belongs to. 

From the opening list you can see all the profiles in your account. You can use the Search text box to filter the athlete list. Once you've found the correct athlete you wish to delete from your account, click the red delete icon from the far right column to permanently delete the athlete profile and its measurements.

The system wants to confirm that you really mean to delete the profile and all its measurements. Click OK to continue and delete. 

You are then taken back to the athlete profile list. If you are ready click the Back button from the top left corner to return to Team management.

Note that removing the player from the team does not delete the profile. It is only removed from the team and the profile is still available on the account.