So when I was asking if it was OP, I was thinking about the PCs using it. Bad guys using it is pretty weak IMO.
A Charisma save is a pretty good save to target for bad guys, but it is a weak save to target against PCs I think, also PCs have tons of ways to break a charm (aside from some races flat having advantage). Also it is not enough damage against PCs, someone casting this could be a side player or a henchman for a much stronger Big Bad, but I don't think this works well at all on a boss.
Definitely not that strong against PCs unless the situation is optimal (an AoO death funnel might be an interesting set up)
Again, I think it fits as a 7th level spell, but it's just not OP. And it's one of those spells where if the caster, or even their allies, get careless it can do more harm then good. As in baddie gets close to caster and caster loses concentration.







