<div class="cp_card">
コンテンツ
  <div class="cp_ribbon10_2">
    <div class="cp_ribbon">Ribbon</div>
  </div>
</div>

.cp_card {
  position: relative;/*リボンをかけたいコンテンツボックスにセット*/
  width: 300px;
  height: 300px;
  background: #ffffff;
  margin: auto;
  padding: 35px 5px 0;
	border: 2px solid #9575CD;
  box-shadow: 0 0 5px rgba(0, 0, 0, 0.3);
}
/*リボンの位置*/
.cp_ribbon10_2 {
  position: absolute;
  top: -6px;
  left: -6px;
}
/*リボンの設定*/
.cp_ribbon10_2 .cp_ribbon {
  padding: 5px 30px 5px 10px;
  color: #ffffff;
  background-color: #9575CD;
  clip-path: polygon(0 0, 100% 0%, 80% 100%, 0% 100%);
}
/*リボンの影*/
.cp_ribbon10_2::before {
  position: absolute;
  content: '';
  top: 100%;
  left: 0;
  width: 6px;
  height: 6px;
  background-color: #5E35B1;
  clip-path: polygon(0 0, 100% 100%, 100% 0);
}