LOGOUT_EVERYONE.ps1

Invoke-Command -ComputerName "TARGETCOMPUTER" -ScriptBlock {
    $sessions = query user
    # Use a more robust regex to grab the ID regardless of the SessionName column being blank
    $sessions | Select-String -Pattern '(?<ID>\d+)\s+(?=(Active|Disc))' | ForEach-Object {
        logoff $_.Matches.Groups['ID'].Value
    }
    foreach ($session in $sessions) {
        $sessionID = ($session -split ' +')[2]
        logoff $sessionID
    }
}

Works best on a domain network.