.fade-underline {
  position: relative;
  display: inline-block;
}

.fade-underline::after {
  content: "";
  position: absolute;
  left: 15%;          
  bottom: -1px;      
  width: 70%;         
  height: 1.5px;


  background: linear-gradient(
    to right,
    transparent 0%,
    rgba(0,0,0,0.4) 20%,
    rgba(0,0,0,0.8) 50%,
    rgba(0,0,0,0.4) 80%,
    transparent 100%
  );
}