<table border="1">
    <tr>
        <td rowspan="2" valign="top">cell 1<div style="align-vertical: bottom">
            want at bottom</div>
        </td>
        <td>cell 2<br>
        <br>
        <br>
        </td>
    </tr>
    <tr>
        <td>cell 3</td>
    </tr>
</table>

<table border=1><tr><td rowspan=2 style="position:relative" valign="top">cell 1<div style="position:absolute; bottom:0">bottom</div></td><td>cell 2<br><br><br></td></tr><tr><td>cell 3</td></tr></table>

<table border="1">
<tr>
    <td rowspan="2" valign="top">cell 1
        <p style="margin-top: 40px">want at bottom</p>
    </td>
    <td>cell 2<br>
    <br>
    <br>
    </td>
</tr>
<tr>
    <td>cell 3</td>
</tr>