>>53656700>a lot of Dark mons are Dark due to their ruthless and aggressive natureDark types are characterized by being cruel, crafty, clever or being born from darker conditions. Look at Murkrow. It's not exactly ruthless, but it's more tricky and mischievous since it's steal shiny things from people or intentionally lead predators into Dark mountains so that they get lost.
>Umbreon>Has zero Dark aspects>Evolves at night>Stalks it prey in the dark and then intentionally cause its rings to glow when attacking as to startled its prey>As a defense mechanism, it's pores can spray poison when agitatedIt fits the dark type mold just fine.