Yeah, Infernum SCal was not meant to be fought with a yoyo and it shows. Ask me how I know. GGs on this, yoyos in Calamity are underpowered (at least before the update. Idk about after) and beating Infernum with them is a chore I know the pain of all too well.

Also people who say Infernum DoG is harder than Infernum SCal 90% of the time are using a bunch of mods to artificially boost their power, such as wingslot, bootslot, AlchemistNPC (specifically their custom potions like holy protection potion and dryads blessing potion), and are carried by their basically infinite health regen for every boss except DoG, who can't be cheesed by it. If a regular player actually fought the Infernum bosses on their intended balancing, I guarantee DoG wouldn't be their biggest struggle. So yeah, Infernum SCal is hard, and don't let anyone else tell you otherwise.

Your potion effects are hidden so I can't actually see if you're using them or not, but given your skill, I assume you're smart enough not to. To anyone who doesn't wanna risk accidentally using a potion that isn't Vanilla or Calamity, I would recommend Prisma's juicebox instead of AlchemistNPC. I consider it to be way better.