Со стилем transform поиграться.
<!DOCTYPE html>
<html lang=ru>
<head>
<style>
.c1{
position: relative;
width: 100px;
height: 300px;
background: green;
}
.c2{
position: absolute;
width: 100px;
height: 300px;
transform: translate(-50px,0) skewX(-20.65deg);
background: red;
opacity: 0.7;}
</style>
</head>
<body>
<div class="c1">
<div class="c2"></div>
</div>
</body>
</html>