Puzzle Pirates does this in a very direct, but effective way. In Puzzle Pirate, ships are ranked based on the rank of individual pirates manning the ship, and ships full of players weaker than you would appear with a blue might rings, while ships stronger than you would appear with red might rings.
If you attack too many blue ringed ships, then you'll be targeted by the Black Ship (El Pollo Diablo (The Devil Chicken)). The Black Ship is a super strong non playable ghost ship, filled with super strong non playable skellies. The ship is nigh invulnerable and undefeatable, with stats that normal ships can't even begin to dream to have. When you lose to the Black Ship, it will take away almost everything you have in your treasure booty, but you gain nothing if you somehow manage to defeat it instead.
This discourages people from getting into unfair fights.
Occasionally though, the black ship becomes a sport for really high ranking players. They try to get targeted by the black ship and try to defeat it for the just for the lulz (though those who dares doing this would usually target friendly ship that is set out for this particular purpose). Black ship hunting is unprofitable, so most players don't do that unless they're really bored. In the rare instances where someone managed to beat the ship, the game permanently upped the difficulty of the ship. Nowadays it's so ridiculously overpowered that you know your fate the moment it engages you.