<div class="box">
  <img src="https://i.pinimg.com/originals/12/1b/f9/121bf994f59266e10aae0210741a4d8d.png" alt="">
  <span class="label">15%</span>
</div>

.box {
  position: relative;
  display: inline-flex;
  max-width: 400px;
}

img {
  width: 100%;
  height: auto;
}

.label {
  position: absolute;
  top: 0;
  right: 0;
  background: yellow;
  z-index: 1;
  clip-path: polygon(25% 0%, 100% 0, 100% 100%, 25% 100%, 0% 50%);
  padding: 3px 5px 0 15px;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 18px;
  color: red;
}