I'll just copypaste the same thing in the video description.

I was testing a facecam setup (one of the last recordings until my PC was completely out-of-order for recording and gaming at the same time) and caught on record the "correct" (or at least the fastest until now) way to 1-cycle the Final Chapter Hyde. Quick disclaimer: "1-cycle", I mean the boss is put into a Overdive Kill mode in the first time his real body is attacked, since there is not a rhythm to follow.

Basically, in a casual playthrough, you must die to the first "Invincible" phase to proceed onto a more accesible one. But, it can be ignored by quickly disposing the regenerating bodies, triggering the Overdive Kill on the boss. So, in order to achieve this the most feasible way, you need to:

1. Have a "Power Surge" ability in your DNA board to achieve maximum damage output, to kill quickly the bodies on the stage
2. Try to maximize kills, as this ability is triggered by kills, by weaponry or overdive. As you always start with no Liberation Gauge, it is an obvius choice to pick an Assault Rifle to do pull the trick.

Yes, the ability trigger it is highly dependant on RNG (or at least, as I'm aware of), but careful movement to dispose of every body once that is active, is not. And yes, it is POSSIBLE to make it without the Infinite Ammo cheat, as you can see in this demo.