I don't know. Witch actually isn't a boss. Well, the JJ2 bosses aren't the most challenging stuff in JJ2. You can make a level much more challenging with enemies and other stuff. If you use an endboss, be sure you put it into the right environment, or you may put some enemies to help the boss because otherwise it can happen that the boss which should in a normal game be a highlight is the easier part of the level. It does just depend how you place it. You can't say what boss is harder. If you don't know what I mean, long time ago I played a single player pack with a secret beach level in it. It had a pit with water in it, a lot of respawning enemies, no ammo and a uterus (the crab from episode 2). Heck, I just wasn't able to defeat that guy. Hope that helped you a bit.