A Size Comparison of Black Holes in the Universe

The design house Kurzgesagt starts on a virtual search for the biggest black hole in the universe. They explain through their distinct animation, the various classifications of black holes from the most little (primordial) to the largest (Ultra Massive).

The largest things in the universe are black holes. In contrast to things like planets or stars they have no physical size limit, and can literally grow endlessly. Although in reality specific things need to happen to create different kinds of black holes, from really tiny ones to the largest single things in the universe. So how do black holes grow and how large is the largest of them all?