I mean. We kinda figured that this would go one of two ways. Either daddy would give a spanking, everyone's happy, daughters are proud of receiving the spanking, daddy gets powers peacefully.
Or daddy wrecks the daughters with or without the spirit's assistance, he regrets giving them an absolute destructive back handed pimp slapping, he gets powers and the spirit has ulterior motives that later may or may not be justified, which if justified then the father eventually heals the spirit's trauma as they grow stronger mutually and if unjustified than we're just giving the daddy a dark edge and the daughters an opportunity of "I can fix him".
Well, there are many other ways this can go, but these are some options right off the bat. And it appears we're headed to the latter one.
Now we have two paths here, either daddy does give the daughters the most thunderous of spankings and he feels horrible about it. Or we skip straight to resolving the issue with the thunder spirit, he rethinks the deal, gives the daddy-o some power maybe and they live happily ever after with no lingering trauma.