Format your HTML properly with <tr>...</tr> around <th>..</th> (& end <th> properly as shown) & add <thead>..</thead> around head & <tbody>...</tbody> around body and add code to auto add missing <td></td>:

$(document).ready(function() {
    // Add missing <td></td> according to number of columns found in head
    var numTd = $('th').length;
    console.log('Number of columns found in head =: ', numTd);
    $('tbody tr').each(function()
    {
        var i = $(this).find('td').length;
        while(i < numTd)
        {
            $(this).append('<td></td>');
            i++;
        }
    });
    
    $('.tree').DataTable();
} );

<link rel="stylesheet" href="https://cdn.datatables.net/1.10.13/css/jquery.dataTables.min.css" />
<link rel="stylesheet" href="https://cdn.datatables.net/responsive/2.1.1/css/responsive.dataTables.min.css" />
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdn.datatables.net/1.10.13/js/jquery.dataTables.min.js"></script>
<script src="https://cdn.datatables.net/responsive/2.1.1/js/dataTables.responsive.min.js"></script>

<table class="tree display responsive no-wrap">
  <thead>
    <tr>
    <th>name</th>
    <th>class</th>
    <th>Remark</th>
    <th>xyz</th>
    <th>zyz</th>
    <th>zyz</th>
    </tr>
  </thead>
  <tbody>
    <tr>
    <td>somethigThing</td>
    <td>somethigvalue</td>
    </tr>
    <tr>
    <td>somethigThing</td>
    <td>somethigvalue</td>
    </tr>
    <tr>
    <td>somethigThing</td>
    <td>somethigThing</td>
    <td>somethigvalue</td>
   <td>somethigThing</td>
    <td>somethigThing</td>
    <td>somethigvalue</td>
    </tr>
    <tr>
    <td>somethigThing</td>
    <td>somethigvalue</td>
    </tr>
    <tr>
    <td>somethigThing</td>
    <td>somethigvalue</td>
    </tr>
    <tr>
    <td>somethigThing</td>
    <td>somethigThing</td>
    <td>somethigvalue</td>
    <td>somethigThing</td>
    <td>somethigThing</td>
    <td>somethigvalue</td>
    </tr>
  </tbody>
</table>