Unite has quests up to HR9, which I think is 11 or 12 stars.
I've soloed every monster in Unite, but some of them are so hard and require multiple deaths that it isn't even fun to solo them (dual Rajang, the different Fatalis). I've made all the weapons and armor I want to make, so right now if we decide to hunt me and my buds just try to collect rares for weird weapons and try goofy shit nowadays (i.e. beating dual Gold/Silver Rath with two hunting horns and a bow). Haven't fired it up since the spring, though, and I can't use Ad-hoc Party because of the worse internet at my new place.