No Straight Roads

After defeating a boss on PARRY difficulty, you will automatically unlock PERFECT PARRY difficulty. The basic idea of this mode is that it is the PARRY difficulty fight with the added rule of one hit death. This means any damage you take will automatically kill you and force you to restart the fight from the beginning. However, sometimes this can be worked around by having Zuke’s upgrade to heal himself when dealing melee damage. So you'll really only ever use Zuke for this difficulty, unless you have some personal interest in using Mayday which just makes this harder. Many, not all, attacks are better parried if you slightly wait a bit for the attack to go off first before you go for the parry. I can't say whether this was intentional, but it is something that helped me a lot. Outside of Eve and Tatiana, you can use Mods and Ultimate Duets to deal extra damage as well. You should have the Shadow Dancer Ultimate Duet equipped for all of these fights since it can deal damage and absorb damage.