JSFiddle - React, Tailwind, and code Playground

HTML

<h4 class="normal">Normal</h4>
<p>Lorem ipsum dolor sit amet</p>

<br>

<h4 class="thickness">Thickness</h4>
<p>Lorem ipsum dolor sit amet duoe</p>

CSS

/* Just a simple CSS Reset */
   * {margin:0;padding:0;}
/* ----------------------- */

h4 {
    font-size: 50px;
    text-decoration: underline;
}

.thickness {
    display: inline-block;
    text-decoration: none;
    border-bottom: 1px solid black;
	margin-bottom: -1px;
}