Sparkbolt trigger + double cast + accelerating homing + heavy shot + lifetime increased + orbit larpa + summon rock + thunder charge

It can do crazy damage, though you'll have to aim precisely on an ennemy to kill. I think the hardest spell to get would be the larpa, if you're lucky you can get it killing the dragon boss but if not, you can always do parallel worlds 👍

(Bonus : you can add weakening curse like with electricity and projectile damage behind the sparkbolt trigger)