<font-awesome-icon icon="fa-duotone fa-angle-left" />
<FontAwesomeIcon icon="fa-duotone fa-angle-left" />
.my-icon {
position: relative;
font: var(--fa-font-duotone);
font-style: normal;
}
.my-icon:before {
position: absolute;
content: "\f104";
opacity:0.5
}
.my-icon:after {
content: "\f104\f104";
}
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 512" style="width: 30px;height: 30px;fill: black">
<path d="M192 448c-8.188 0-16.38-3.125-22.62-9.375l-160-160c-12.5-12.5-12.5-32.75 0-45.25l160-160c12.5-12.5 32.75-12.5 45.25 0s12.5 32.75 0 45.25L77.25 256l137.4 137.4c12.5 12.5 12.5 32.75 0 45.25C208.4 444.9 200.2 448 192 448z"/>
<path style="opacity: 0.5" d=""/>
</svg>
<i class="fa-duotone fa-angle-left"></i>