I am currently playing an Arcane Trickster that has a Flame Tongue Rapier and access to Booming Blade.
So I have:
I am considering getting access to the Poisoner feat and Hex, adding Poison and Necrotic to the mix (with a ridiculous set-up sequence, I know).
This would leave me at 5 damage types in a single attack.
Is it possible to have more, across any class/subclass/multiclass (i.e., you're free to start with a new blank character)?
You can assume to get to level 20, and have access to items in the PHB, DMG, Xanathar, and Tasha. As in the case of my character, set-up can be spread over multiple rounds. Outside help is allowed, but I would prefer not.