Quote Originally Posted by MaxWilson View Post
Does it even matter? Eldariel has clearly already won the thread by reminding us of Hydra Shapechange/True Polymorph. There is no integer so large that a hydra cannot attain that number of attacks.
I agree that this is almost certainly the way to the most attacks, but I will raise a couple of objections.
I would like to point out that the Hydra doesn't have a method of healing itself (No allies is assumed), and the net damage per Hydra head is 15 (Take 25, heal 10). A Hydra has 172 hp, so you can only take the damage 10 times, for a net total of 15 heads, which becomes 30 attacks with action surge, and 31 with a bonus action attack from some means. (Battlemaster maneuvers come to mind). With Second wind, which you have from fighter levels you should be able to get one more head, and 2 more attacks.

In the case of Shapechange and True Polymorph, you're going to have to make concentration checks for each one, and for True Polymorph you don't have action surges. True Polymorph and Magic Jar as permanent buffs that you had prior to this feels against the spirit of it.

As a last point, you don't really have a reliable way to deal exactly 25 damage to yourself. This certainly seemed to be a point of contention for the OP in the samurai case, and if you do figure a way to deal exactly 25 damage to yourself each time, we're still talking about at minimum 12 rounds of setup, when the other greatest amount of setup is 2 rounds.