Kylo gives an offhanded compliment to some work Hux did recently, and accidentally discovers Huxs praise kink through his barely withheld reaction. its not just praise, but daddy kink rooted in craving praise from someone with seemingly unbeatable power. Kylo being younger only adds layers of arousing shame; he has Hux submissive just by telling him stuff like ‘i’m so proud of you’ after meetings or speeches. Hux ends up using his professional efforts just to make Daddy Ren proud & reap rewards~