JSFiddle - React, Tailwind, and code Playground

HTML

<figure class="banner">
  <img class="banner__img-real"src="https://images.hdqwalls.com/download/triangles-colorful-background-nz-1920x1080.jpg" alt="">
  <img class="banner__img-shadow"src="https://images.hdqwalls.com/download/triangles-colorful-background-nz-1920x1080.jpg" alt="">
</figure>

CSS

.banner {
  position: relative;
  margin: 50px;
  width: calc(100% - 100px);
}

.banner__img-real {
  display: block;
  max-width: 100%;
  position: relative;
  z-index: 2;
  border-radius: 10px;
}

.banner__img-shadow {
  position: absolute;
  z-index: 1;
  border-radius: 10px;
  width: calc(100% - 20px);
  top: 10px;
  left: 10px;
  filter: blur(20px) brightness(2) saturate(1.5);
}

body {
  margin: 0;
  background-color: #333;
}