I want to know what would be the best optimization for a demon (maybe also devil) hunting class. At the moment my considerations are a ranger with evil outsiders as his favoured enemy, or a paladin. I'm open to other classes; just to let you know I want to play it in an inquisitorial style, trusting few and ready to wander the world to root out evil where it hides.
Depends, demon hunting or demon killing?
Demon killing is paladin. Probably archer paladin.
Oddly enough however, the paladin really dosen't have that much to find, track, and root them out except detect evil. Which is fairly good if they are close and don't have any protection from that.
For the finding, tracking, and rooting them out; your best bet would be either ranger or inquisitor. Probably inquisitor.
Favored Enemy and Smite are pretty comparable numbers-wise. Smite is more generally useful but FE doesn't have a per-day limit.
If the game is heavily focused on Evil Outsiders, you're probably better off with Ranger in the long-run for damage and tracking.
If the enemies you face are a little more varied, Paladin's probably the better choice, as well as the better defensive option.
Full casters are also always a good choice.
Combat wise a paladin will probably be the strongest. He not only gets smite evil, but a lot of defensive abilities that are very helpful vs evil outsiders. If you are looking for the class that will most likely be standing at the end of the battle with a demon a paladin is hard to beat. Their problem is that don’t have much in the way of investigation. If the demon is right in front of them they are good, if they have to uncover it they are at a disadvantage. Detect evil is great for spotting the disguised demon, but won’t do much good in locating the demon.
A ranger with favored enemy evil outsider does pretty well against demons. His favored enemy bonus also applies to several important skills that will be useful. The problem with Ranger is that while he has a lot of skills, and some of them are useful in this situation he does not have the social skills needed. He does get perception and survival so he can spot and track demons better than anyone else. What he does not get is diplomacy to gather information, or sense motive to figure out when he is being deceived. Also most of his spells are nature oriented and not as useful for dealing with demons.
An inquisitor has good combat abilities especially once bane kicks in. Judgments can give him some very useful abilities tailored to the specific demon. Their selection of spells can be tailored to be very effective vs demons. Protection form evil for example is almost ridiculously effective vs. demons. They also have a lot of divination spells that will be helpful. When it comes to investigation they are unmatched. They can track like a ranger; detect any alignment not just evil, and the ability to discern lies. They have all the investigation skills and a bonus to sense motive that no one is going to be able to match. The only problem they have is that a lot of their abilities have limits on how often they can be used.