Nice! I have it too. For kulve I would say definitely protective polish. You can spam the charge run attack and protective polish stops the fairly hefty sharpness cost.
For other fights, I'm less sure...
Here it is.
Taroth Crest Thunder with affinity aug + Mighty jewel
Rath Soul Helm beta + 2× bolt jewel
Rath Soul Mail beta + mighty jewel
Kulve Taroth Rage beta + tenderizer and bolt jewel
Kulve Taroth Malice beta + critical and bolt jewel
Kulve Taroth Wrath beta + critical and bolt jewel
Exploiter charm II
You can swap bolt jewels with 5x attack jewels if you have or 3 with iron wall and one mighty jewel with guard up if you need some defensive skills.
This weapon has decend amount of blue and since it's a lance then you always be hitting a weak spot and sharpness doesn't go down that fast.
I'm gonna make some changes when I get Dantes pants
I also have version with 90% affinity without weakness exploit so doesn't matter if you hit weakspot or not you crit 90% of the time.
You just need to replace tenderizer jewel with mighty jewel exploier charm with master's charm 3 and all the bolt decos with expert jewels. It does a bit less damage but you will crit no matter where you hit =)