With the exception of the final boss, Carnivorous Mutae is easily the hardest to beat. This is largely due to unpredictable nature of it’s attacks. Even so, with a good tactic and some luck this isn’t a terribly difficult fight.
For every fight I strongly suggest using the gauntlets. Not only are they fast and deal decent damage, the charged punch attack has invincibility frames that make players immune to energy based attacks. From there, no player should need potions outside of the last fight and upgrades are helpful, but only important if you want to win without taking damage.
Similar to the Golem King, Carnivorous Mutae follows a predictable pattern. The first attack always spawns adds, followed by vines popping out of the floor, it jumping, swirling bullets and then another round of adds, with the cycle, minus add summoning, continuing until it dies. The trick to this fight is luck and knowing where to stand.
Like, with the exception of a couple attacks, standing in the middle, on either side, is relatively safe. Likewise, charged punches are or at least were immune to physical attacks, though getting hit like that will void a perfect run. However, it’s completely safe to dodge a jump like that, provided a vine doesn’t hit you during said jump. Outside of that, take it slow, kill adds when you can and abuse invincibility frames during the bullet sections.
For those looking to do a perfect run, I never figured out a way to consistently dodge vines popping out of the ground. I found they appear around your current location, so going a single direction seems to work well at avoiding them, with enemy placement being completely luck based. Besides that, the end goal should be to kill it before a second vine attack happens. This is completely possible and the best way to reduce the luck required to win the fight.