SharePoint Online: Remove User from Subsite Permission using PowerShell

Requirement: Remove user from a SharePoint Online subsite

How to Remove a User from SharePoint Online Subsite?
To remove a user from SharePoint Online subsite,

1. Remove user from all groups of the site
   
2. Remove user from direct permissions of the site (if any)
   

SharePoint Online: Remove User from Subsite Permission using PowerShell
Here is how to remove user permissions in SharePoint Online using PowerShell

#Load SharePoint CSOM Assemblies
Add-Type -Path "C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\16\ISAPI\Microsoft.SharePoint.Client.dll"
Add-Type -Path "C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\16\ISAPI\Microsoft.SharePoint.Client.Runtime.dll"
  
#Set parameter values
$SiteURL="https://crescent.sharepoint.com/sites/marketing/2018"
$UserID="salaudeen@crescent.com"
 
Try {
    #Get Credentials to connect
    $Cred= Get-Credential
   
    #Setup the context
    $Ctx = New-Object Microsoft.SharePoint.Client.ClientContext($SiteURL)
    $Ctx.Credentials = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($Cred.Username, $Cred.Password)
  
    #Get the web
    $Web=$Ctx.Web
    $Ctx.Load($Web)
    $Ctx.ExecuteQuery()
 
    #Frame Login Name
    $LoginName = "i:0#.f|membership|"+$UserID
 
    #Get the User to Delete
    $User = $Web.SiteUsers.GetByLoginName($LoginName)
    $Ctx.ExecuteQuery()

    #Remove User from All Groups of the site
    $Ctx.Load($User.Groups)
    $Ctx.ExecuteQuery() 
    ForEach($Group in $User.Groups)
    {
        $Group.Users.RemoveByLoginName($LoginName)
        Write-host -f Yellow "`tRemoved User from the Group:" $Group.Title
    }
    $Ctx.ExecuteQuery()
 
    #Remove the user from direct permissions, if any
    $Ctx.Load($Web.RoleAssignments)
    $ctx.ExecuteQuery()

    ForEach($RoleAssignment in $Web.RoleAssignments)
    { 
        $Ctx.Load($RoleAssignment.Member)
        $Ctx.executeQuery()
 
        #Check direct permissions
        if($RoleAssignment.Member.PrincipalType -eq "User")
        {
            #Is the current user is the user we search for?
            if($RoleAssignment.Member.LoginName -eq $LoginName)
            {
                #Remove User from web Permissions
                $Web.RoleAssignments.GetByPrincipal($User).DeleteObject()
                $Ctx.ExecuteQuery()
                Write-host -f Yellow "`tRemoved User from Direct Permissions of the Web!"
            }
        }
    }

    Write-Host "User: '$UserID' has been Removed from the site Successfully!" -ForegroundColor Green
}
Catch {
    write-host -f Red "Error:" $_.Exception.Message
}

To remove a user from site collection, use: SharePoint Online: Remove User from Site Collection using PowerShell