JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
<li>a</li>
<li>a</li>
<li>a</li>
<li>a</li>
</ul>

CSS

ul li {
  line-height: 30px;
  height: 30px;
  list-style: none;
  width: 200px;
}
ul li:not(:last-child) {
  border-bottom: 1px solid green; 
}