So that'd be CON +7, WIS +4, CHA +2? Works for me.
It was you who proposed the lightning attack not me.
I was just thinking it'd use it like a pitchfork to stab or toss opponents:
The original monster could make three Multiattacks per round: two piercing attacks with its tusks and one toss attack with its tail.
So I'm thinking if its Multiattack could choose any three attacks from a piercing Tail Trident, piercing Gore, "
I'd be fine giving the Juggernaut version a tail zap attack and maybe a cone of acid from its trunk, but that'd feel like it strays too far from the original monster.
Still, lightning resistance or immunity is a common feature of 5E demons so I
guess we'd better keep it.
Plus they get cold & fire as standard.
Hmm, how about we give them resistance to acid, cold, fire, lightning? There are demons around that CR have special defenses against 4 energy types, like the CR 6
Babau.
The Damage Resistance to bludgeoning, piercing, and slashing from nonmagical attacks feels more of a stretch to me.
The original monster didn't have any weapon immunities. Demons are traditionally tough against fire and the like in D&D but a fair few of the weakest or "part demon" creatures are subject to normal weapons.