I am currently using 'Lilacrcor'.

DIfferent weapons have different effects, so I'm not sure exactly what you mean by "best". But here's a good place to browse different weapons of BG2 : http://mikesrpgcenter.com/bgate2/weapons/twohandedswords.html

This site is great for quick summaries of items, but if you want more detailed descriptions, Gamebanshee is the way to go : http://www.gamebanshee.com/baldursgateii/equipment/twohandedswords.php

Game banshee makes you click each item, which is usually a hassle when you are browsing on smart phones.

You won't find a better two-handed sword before chapter 6 but if i annoys you it's ok to use a weaker weapon.