JSFiddle - React, Tailwind, and code Playground

HTML

<div class="efeito">
  Lorem ipsum dolor, sit amet consectetur adipisicing elit. Sed voluptate dignissimos odit quod velit, natus vero ut ratione libero nulla!
</div>

SCSS

html, body {
  width: 100%;
  height: 100%;
  margin: 0;
  padding: 0;
}
.efeito {
  background: #f00;
  width: 100%;
  position: absolute;  
  
  &:after {
    content: '';
    position: absolute;
    top: 100%;
    left: 0; 
    right: 0;
    padding-bottom: 10%;
    background: #f00;
    clip-path: polygon(0% 0%, 100% 0%, 50% 50%);
  }
}