JSFiddle - React, Tailwind, and code Playground

HTML

<div>
  <ul>
    <li><span>aaabbbccc:</span><i></i></li>
    <li><span>aaabbb:</span><i></i></li>
    <li><span>aaa:</span><i></i></li>
  </ul>
</div>

CSS

ul, li {
  margin: 0;
  padding: 0;
  list-style: none;
}

div {
   width: 200px; 
}

div li {
  display: flex;
}

div li i {
  border-bottom: 1px solid;
  flex-grow: 1;
}