I've counted 13 bosses across all the worlds and plotlines. Most of these are monsters (or disturbed local wildlife, depending on your point of view!). The only enemy character bosses are: The Second Sister The Ninth Sister Taron Malicos Darth Vader (but you'll be running from, not fighting, him!) The Second Sister is by far the most challenging opponent you'll come up against. It took me a long time to defeat her.