Well right this second I've got Hallowed Armor with the mage helmet and my weapon is, like,
https://terraria.gamepedia.com/Spirit_Flame
This.
I don't know what all in my kit is bumping it up a notch if anything but I have it reforged to Mythical and it says in-game that it does 126 damage a hit.
There's a delay between casting and firing and it's not the fastest fire rate but playing on a trackpad auto-targeting is nice and that damage stat is
hilarious.
My strat is hop onto the Basilisk mount (not as fast as a full-blast minecart or running on asphalt and not as air oriented as wings but definitely accelerates faster and jumps okay-ish) and running back and forth on a small-ish strip of flat arena with like five Campfire/Heart Lantern/Star in a Bottle combos lining it. And just drinking every conceivable buff potion I can get my hands on that could apply to the battle while riding back and forth trying to dodge. If I can remember I also line the general path with
https://terraria.gamepedia.com/Nimbus_Rod
https://terraria.gamepedia.com/Clinger_Staff
And if I'm really brainy
https://terraria.gamepedia.com/Queen_Spider_Staff
And I have like three regular spider summons from the normal Spider Staff out at once from stacking multiple summoner buffs even if my current armor isn't in the class.
I've alternately tried shooting at it with the Megashark and Cursed Flame Bullets a couple of times but like
Once Phase 2 on Spazmatism kicks in I'm already at like a third of my health and then from there I'm just rapidly bowled over.
*sigh* Maybe I just need to kit out and lengthen my skybridge instead of trying to use a wiggle arena, I just didn't want to risk a Wyvern piling on.