You can play an anti-paladin. I posted it a while back, but here goes again.
1) create a paladin
2) name your character "anti-paladin" (drop the quotation marks)
2) go into Shadowkeeper and change the following values:
Alignment = Chaotic Evil
Kit = none (although this may vary -- haven't tried any anti-paladin's with kits)
Race = 0x98 (unknown value)
Have fun. You are now playing a Chaotic Evil Paladin and you can use the Unholy Reaver if you pick it up.
You now can play
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Most Subtle Official Straightman of the Laughing Hyenas -- Grammarian Brigade.