Ever since the anti-paladin class came out, I have always wanted to create a character that pretty much used the powers of evil in order to crush other forms of evil. Think of it as a radical paladin who dabbles in the 'forbidden arts', believing that the best way to combat evil is to use evil against itself. The paladin in question willingly puts their soul on the line in the hopes that obtaining greater power through patrons like demon lords will help them to quell other forms of wickedness in the world. They are keenly attuned to the dark desires that lie within every creature's heart, and as such, they are exceptionally gifted in understanding how to thwart the plots and plans of tyrants, murders, and cut-throats alike. They disdain the methods of 'goodly' warriors (like paladins), believing that their methods are far too conservative to make any real progress against the forces of darkness.
Such anti-paladins have no reservations about lying, torturing, or betraying other creature's in order to get the job done. Where a normal paladin might scoff at the notion of breaking their word or harming a captured prisoner, the anti-paladin understands the necessity of doing 'small evils' in order to obtain a greater good. After all, what good does it do to keep your honor if evil is allowed to thrive because of it?
Because of this mentality, such anti-paladins are far more difficult to predict and manipulate, which is seen as a common 'weakness' among most other 'good-aligned' creatures. Patrons of these 'radical paladins' often view their servants as amusing, misguided, but useful tools, and often employ them to thwart the plans of other rival deities. In some cases, such deities can even call upon these anti-paladins to test the worth of their own followers, or use the anti-paladin as their personal enforcer to punish those who have displeased them.
[Side note: Yes, I realize that this is starting to sound like an introduction to a new archetype, but to be honest, I really do hope that paizo eventually starts releasing 'expansions' for some of the more underused classes like the anti-paladin]
Anyway, this was just one idea I had for giving the anti-paladin a little more flare, but I was also curious to see if anyone else had any other cool ideas for expanding upon the class as well. Basically what I'm looking for are creative ideas that support the 'cool' kind of evil rather than the 'eat babies and kick puppies' kind of evil. After all, if a hero fails, then perhaps it is time to call upon a villain.