JSFiddle - React, Tailwind, and code Playground

HTML

<div class="green">
    <div class="red">АКЦИЯ</div>
</div>

CSS

.green {
    background:green;
    width:300px;
    height:300px;
    position:relative;
    overflow:hidden;
}

.red {
    transform: rotate(45deg);
    width:250px;
    background:red;
    position:absolute;
    color:#FFF;
    padding:10px;
    top:20px;
    right:-100px;
    text-align:center;
}