Hawk Diesel
Adventurer
I like this for a ranger capstone:
Foe slayer: At 20th level, you become an unparalleled hunter of your enemies. Versus your favored enemies you cannot be surprised and have advantage on all attack rolls, ability checks (including initiative) and saves. Favored enemies have disadvantage on attack rolls.
It has the flavor of knowing your favored enemy so well that you get foresight against them. You know your favored enemy so well that you can predict what they are going to do and when they are going to do it.
While I understand that the Favored Enemy mechanic is one of the more unique and central aspects of the class, it relies too greatly on DM fiat to be useful.
What I mean by that is if your DM chooses to throw favored enemies into your battles, then it's great. If the DM doesn't, then it's useless. IMO, class abilities should not be the sole purview of the DM.