You don't
Basically all people get "tough" now fast, by the looks it seems more like the Kangaxx was meant to be killed after, say, Underdark, when you are higher lvl and can buy some better gear from Mart, as well as Cromwell can build some better items for you.
But as far as 1-hand swords go, in SoA there doesn't seem to be any which is good enough for Kangaxx or his ilk.. As dual wielding sword using char, I really have no "tools" to smack him. I am about to get the Grom Faeyr, Jaheira has +5 sling, maybe some staff I had as well, that's all.. Have Carsomyr but no paladin heh, no biggie tho.