| Skylancer4 |
If you are talking a very heavy undead setting (think Resident Evil, where pretty much all enemies are undead) hands down Ranger base with the undead FE/terrain tricks. Get large static bonuses that have no daily use/limits and for the occasional enemy that isn't undead use a wand of the spell that treats the target as if it were a FE. I want to say the 'best' bonus stacking build is ranger/horizon walker/rogue(rogue trick terrain), should be able to find it on the boards.
Next would probably be a cleric, then paladin in such a setting. They can all do very well vs undead (channel energy) but sometimes targeting can be problematic (burst) and they have daily limits.
The less likely you are to run into undead the utility of the cleric/paladin becomes more favorable.
Also an inquisitor might do well if you haven't looked at it. Also a gravewalker witch could be an interesting play (possess the undead to fight the others).