How to Remove termset using powershell script

You need to have the initial variables at hand as well as the Term Store Name (in the @store variable), to make this work.

if ((Get-PSSnapin "Microsoft.SharePoint.PowerShell" -ErrorAction SilentlyContinue) -eq $null) 
{
    Add-PSSnapin "Microsoft.SharePoint.PowerShell"
}

# Initial Variables
$SiteCollectionUrl = "http://portal/"
$termGroupName = "Intranet"
$termSetNames = @("TermSet1", "TermSet2")

function RemoveTermSet([Microsoft.SharePoint.Taxonomy.TermStore]$store, [string]$groupName) 
{
  if ($group -ne $null) 
  {
    $group.TermSets|foreach{
      if($termSetNames -ccontains $_.Name)
      {
        Write-Host $_.Name "will be deleted"
        $_.Delete()
        $store.CommitAll()
      }
    }
  }
}

$session = Get-SPTaxonomySession -Site $SiteCollectionUrl
$store = $session.TermStores["Managed Metadata Service"]
$group = $session.TermStores.Groups | Where-Object {$_.Name -eq $termGroupName}

RemoveTermSet @store $termGroupName
$store.CommitAll()