<div class="el"></div>

.el {
	position: relative;
	padding: 50px 100px;
	border-radius: 15px;
	background-image: linear-gradient(to right, green calc(100% - 70px), blue);

	&::after {
		content: '';
		position: absolute;
		top: 100%;
		right: 13px;
		width: 100px;
		height: 19px;
		background-color: red;
		clip-path: polygon(0 0, calc(100% - 18px) 0, 100% 100%);
	}
}