SF_10.1, SF_10.2, SF_11.0, SF_11.1, SF_11.2, SF_12.0, SF_12.1, SF_12.2, SF_13.0, SF_13.1, SF_13.2, SF_13.3, SF_14.0, SF_14.1, SF_14.2, SF_14.3 - https://docs.sitefinity.com/for-developers-delete-users

DeleteUser.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Telerik.Sitefinity.Security;
using Telerik.Sitefinity.Security.Model;

namespace Telerik.Sitefinity.Documentation.CodeSnippets.DeepDive.Security.Users
{
    public partial class ManagingUsersSnippets
    {
        public static void DeleteUser(string username)
        {
            UserManager userManager = UserManager.GetManager();
            UserProfileManager profileManager = UserProfileManager.GetManager();

            User user = userManager.GetUsers().Where(u => u.UserName == username).SingleOrDefault();

            if (user != null)
            {
                SitefinityProfile userProfile = profileManager.GetUserProfile<SitefinityProfile>(user);

                if (userProfile != null)
                {
                    profileManager.Delete(userProfile);
                }

                userManager.Delete(user);
            }

            profileManager.SaveChanges();
            userManager.SaveChanges();
        }
    }
}