button[class*=plg_system_webauthn_login_button] {
  max-height: 3rem;
  padding: .25rem;

  span[class*=icon] {
    display: inline-block;
    width: 1em;
    font-size: 1.25em;
    text-align: center;
    vertical-align: sub;
  }

  img[class*=icon] {
    display: inline-block;
    height: 2.5rem;
    padding: 0 .25em 2px;
    font-size: 1.5em;
    text-align: center;
    vertical-align: middle;
  }

  span[class*=icon]:not(:last-child) {
    margin-right: .5em;
  }
}

• [F] button.scss
  Delete