Level 22 only. one shot kill so i doubt the stats are high?
It's not necessarily the biggest factor, but if you're fighting much weaker opponents the fair fight will be reduced a lot so that will become clear.
You can check fair fight in the chain logs next to the attack you do and you'll be able to gauge how weak a target is. Being able to one-shot someone isn't necessarily an amazing indicator of the fair fight bonus they're likely to give you because it's based on a 'score' that takes into account the balance of your stats as well. You might just be set up well stat-wise to fight that particular target, even if they have a high 'score' and therefore give a good fair fight multiplier.