JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container" dir="rtl">
	<div class="content" dir="ltr">
		<div class="float-end"></div>
	</div>
</div>
<div class="container" dir="ltr">
	<div class="content" dir="rtl">
		<div class="float-end"></div>
	</div>
</div>
<div dir="rtl">
	<div class="container" dir="ltr">
		<div class="content" dir="rtl">
			<div class="float-end"></div>
		</div>
	</div>
</div>

CSS

*{
	box-sizing: border-box;
	margin: 0;
	padding: 0;
}
.container{
	height: 200px;
	background: red;
}
.content{
	width: 300px;
	height: 200px;
	background: rgba(0,0,0,.2);
	margin: 0 auto;
	border: 1px solid rgba(0,0,0,.5);
	position: relative;
}
.float-end{
	width: 100px;
	height: 100px;
	position: absolute;
	top: 50%;
	left: 50%;
	-webkit-transform: translate(-50%, -50%);
    -ms-transform: translate(-50%, -50%);
    transform: translate(-50%, -50%);
}

[dir="ltr"] *:not([dir="rtl"]) .float-end,
[dir="ltr"] > .float-end{
	border-left: 100px solid rgba(255,255,255,.8);
	border-bottom: 50px solid transparent;
	border-top: 50px solid transparent;
}
[dir="rtl"] *:not([dir="ltr"]) .float-end,
[dir="rtl"] > .float-end{
	border-right: 100px solid rgba(255,255,255,.8);
	border-bottom: 50px solid transparent;
	border-top: 50px solid transparent;
}