My experience with a yellow banded possum wrasse is quite different than other posters. I have had mine for many years and is one of my favorite fish. Although reclusive during mid-day sun, he comes out and specifically interacts with me when the light levels are lowered. He seems to hang out with a single ocellaris clown with absolutely no aggression between the two. I have had others bully it, but it seemed to always defend itself and the aggression would stop. With that said, do not mix it with an aggressive species. He does not eat flatworms, but aggressively seeks out pods. The possum wrasse swimming behavior is one of the more interesting characteristics, more like a hummingbird or underwater ROV. He generally keeps the caudal fin collapsed so it it arrow shaped and rarely uses it for propulsion. Don't expect a dazzling color from a yellow banded, but personality galore.
Fish that initially bullied it were red hawkfish (little), royal gramma (more than a little), midas blenny (only when the possum challenged the midas, but that is the typical behavior of a midas), and a pygmy hawkfish (very little interaction). My Potter's angel does not bother it at all.