Bootstrap class: .align-items-*-end

<div class="d-flex align-items-end">
  <div class="p-2">Flex item 1</div>
  <div class="p-2">Flex item 2</div>
  <div class="p-2">Flex item 3</div>
</div>

<!-- responsive variations -->
<div class="d-flex align-items-sm-end">...</div>
<div class="d-flex align-items-md-end">...</div>
<div class="d-flex align-items-lg-end">...</div>
<div class="d-flex align-items-xl-end">...</div>

Preview

Flex item 1
Flex item 2
Flex item 3

More in Bootstrap Flexbox