What are the best profitable online businesses?

With the digitalization of the world, online businesses are booming like never before, and the trend is possible to carry on in the coming years. Online business is perhaps the best choice for Entrepreneurs to start their new business. Because an online business can begin with a small investment and have very lesser expenses than a typical traditional business. Also, with traditional business, the reach is limited to the city or the country depending on the proportions of the business and the cash the owner is keen to rope in. Though, with online business, we can aim international audience with easiness. Can you guys list down the best profitable online business?