<div class="alert alert-success fade show" role="alert">
  Félicitations 🥳
</div>

<div class="alert alert-warning alert-dismissible fade show" role="alert">
  Message plutôt important !
  <button type="button" class="btn-close" data-bs-dismiss="alert" aria-label="Close"></button>
</div>

.demo {
  width: 100%;
}

.demo > .alert:last-of-type {
  margin-bottom: 0 !important;
}