Rayalot is right here, there are not immunity stats for these effects. Maybe one day we will need them. what do you think?
I still feel like there should be a blanket "CC immune" for creatures which provides immunity to a particular set of effects, including stun, fear, confusion, devour, and knockback, with some prepared ease of adding more. L and larger creatures could be defined by all having this trait. Depends on if you think you'll need immunity to only some effects on certain creatures, but you could assign some abilities to have an override to CC immunity (like harvestman self-fear, or major taunt if taunt is added to the list).
Depends on what you and the other developers deem most efficient on the back-end.