<tr role="row" class="odd">
<td width="10%">1152012985</td>
<td width="13%">22:02:34</td>
<td width="12%"><img src="/images/cur_DOGE.png" width="18px" height="18px"><span>DOGE</span></td>
<td width="18%"><a class="nick">rijiy</a></td>
<td width="13%">0.006</td>
<td width="11%"><48</td>
<td width="10%">39.8071</td>
<td width="13%" class="green">+0.00600000</td>
</tr>
<table> <tr role="row" class="odd" id="myList">
<td width="10%">1152012985</td>
<td width="13%">22:02:34</td>
<td width="12%"><img src="/images/cur_DOGE.png" width="18px" height="18px"><span>DOGE</span></td>
<td width="18%"><a class="nick">rijiy</a></td>
<td width="13%">0.006</td>
<td width="11%"><48</td>
<td width="10%">39.8071</td>
<td width="13%" class="green">+0.00600000</td>
</tr> </table>
let cellsCount = document.getElementsByTagName('table')[0].rows[0].cells.length-1 // посчитать количество ячеек
document.getElementsByTagName('td')[cellsCount] // вернет элемент с последним индексом
<table>
<tr role="row" class="odd">
<td width="10%">1152012985</td>
<td width="13%">22:02:34</td>
<td width="12%"><img src="/images/cur_DOGE.png" width="18px" height="18px"> <span>DOGE</span></td>
<td width="18%"><a class="nick">rijiy</a></td>
<td width="13%">0.006</td>
<td width="11%"><48</td>
<td width="10%">39.8071</td>
<td width="13%" class="green">+0.00600000</td>
</tr>
</table>
document.querySelector('.odd').lastElementChild.classList // ["green", value: "green"]
document.querySelector('.odd').lastElementChild.classList[0] // "green"