METAL GEAR RISING: REVENGEANCE

Of all the boss fights that you need to complete with "No Damage", Mistral is the easiest.

WHAT YOU WILL NEED FOR THIS TROPHY:

1. A backup save (just in case )
2. Basic understanding of the parry system
3. Patience

WHAT WILL MAKE THIS TROPHY EASIER TO OBTAIN (but not necessary):

1. A maxed Muramasa blade
2. A maxed Sai (this will stun her, but it can be challenging to get the damn thing to hit her with all the other dwarf gekkos running around )
3. Basic understanding of the "Offensive Defensive" maneuver (direction + Square + X)

WHAT WILL MAKE THIS TROPHY NEARLY IMPOSSIBLE TO NOT OBTAIN (in conjunction with the items above):

1. Infinite Wig B (for unlimited Ripper Mode)
2. Custom Red Armor (increased damage)

The reason why this fight is the easiest is because it is broken up into 3 parts, with each part initiating a checkpoint save. This breaks the fight up very easily, and allows you to restart from said checkpoints if you take damage during any of the fights 3 stages.

For example, if you get through the first stage with no problem, but during the second stage you get hit, press the start button, and choose the "Restart" option - you will be back during the second stage of the fight with that nasty hit being wiped from the games memory.

Please note you need to be on at least Hard Difficulty for this No Damage boss fight to mean anything at all.

During the first stage of the fight I basically just used the Ninja Run Cut-Em-Up paradigm, immediately initiating Ripper Mode, circling Mistral to deal her damage, but also taking out those annoying dwarf gekkos. When the option comes up to use Blade Mode I didn't take it - I just kept cutting her up. With Custom Red, a maxed Muramasa and in Ripper mode you will get her to 70% health literally in seconds.

Then a cut scene will be initiated where Mistral hog-ties your leg. Unlike the previous difficulties, you need to cut a specific part of the pole arm in order to get through this, so be warned.

After the cut scene you will end up on a pipe. Initiate Ripper Mode again, and run towards her - she will take higher ground and start throwing those dwarf gekko bodies at you. You can either parry OR stand underneath her - your call.

She will jump down, and you can start cutting her up again. Here is where the parry move becomes critical: unlike the first stage, you are very limited with your movements. Parrying her attacks is a necessity. If you are having difficulty with the parry move, I suggest playing on Normal and getting to the Monsoon fight - that guy will make you a parry savant .

Get Mistral down to ~50%, and another cutscene will take place, as well as another checkpoint save. This is basically a longer version of the first stage of the fight. I went with Ninja Run Cut-Em-Up again, while in Ripper Mode, however be careful: she is standing next to a few explosive barrels that, if you cut, will knock you back a few feet AND take away your "No Damage" bonus (thus negating the trophy). If that happens, restart from the checkpoint.

This is where I found the Sai helpful - it will stun her, eliminate the distance between her and you AND do damage. Wins all around. Unfortunately you NEED to take care of most of the dwarfs first, or you may target them instead, and leave yourself wide open .

The Pincer Blades are also devastating to her, however I rarely had a moment to effectively use them, as those damn dwarfs would jump on me leaving me vulnerable OR hit me. Use those with caution.

Also, this is where the dodge (Offensive Defensive) move really comes in handy. If you see her glowing gold (unblockable moves) try to get in close and use the dodge - it will give you a second of invulnerability AND deal her a decent amount of damage.

Once she gets to ~10%, a QTE will occur. Initiate that, and you are in the clear as long as you took no damage. If you see that you have, restart from the checkpoint and try again.

If for some reason you botched up and didn't notice you took damage in one section, go to your backup save. You may have to start from the beginning of the battle, but at least you don't have to run through the level again.

Questions, corrections and neg vote justifications below.

Mistral is one of the easiest (if not the easiest) of the bosses to avoid taking damage from, she is easily telegraphed, stunned and it doesn't take much to damage her, not only that but she has 3 CHECKPOINTS! This means if you take damage after one of these you can reset to last checkpoint without having to replay the entire battle from the start.
Obviously you have the option to do it right away or on a second playthrough when you have unlocked more equipment, both are easily achievable and I will explain how to do so both ways.

First Playthrough -
Phase 1 (first checkpoint): This part is possibly the easiest, you'll just need to run at her and perform a sliding kick (triangle, triangle) after this you can follow up with a few regular slashes until the screen goes slightly blue hinting for you to use Blade Mode, once in Blade Mode hit the blue part of her staff and repeat this process until the second phase of the battle.

Phase 2 (second checkpoint): This part plays much like the previous however Dwarf Gekkos will become a bit more annoying due to it being a narrow path, they may sponge your attack and force you to lock onto them, from the start make a dash right for her and do the previous sliding kick followed up by slashes strategy, immediately afterwards be prepared to parry (or run away), she doesn't always follow up with an attack but if she does you will need to block it, after that (or if she doesn't attack) follow up with the exact same moves, it shouldn't take more than 3 repeats of this process to begin phase 3.

Phase 3 (third checkpoint): This part can be made difficult by the occasional seizure of the camera (usually caused by the lock-on on Mistral when she jumps disappearing then re-appearing multiple times), this stage can be completed exactly the same way as the first however you will spend more time running around avoiding her attacks (if you keep a distance you should never need to parry) occasionally she will jump high and throw bombs at you (Dwarf Gekkos), just run around in circles, they aren't hard to avoid (I've never been hit by one in my many playthroughs...)

Second Playthrough -
Phase 1 (first checkpoint): This is made far easier when you have access to Ripper Mode, Sai and the Staff, you can opt to use the Blades too but there's really no need. In this first phase you'll want to just activate Ripper Mode and spam your Staff, this phase will end in seconds (you may still need to Blade Mode her staff depending how fast you do it, if you do she'll enter the next phase after hitting her once after that).

Phase 2 (second checkpoint): This time you want to activate Ripper Mode and use your Sai, not only to launch at her but to perform the drop attack too, be prepared to do an ariel parry just in-case but probably about 90% of the time she doesn't do a follow up attack, repeat that process again (even though you wont have the energy for Ripper Mode this time) this will finish this phase.

Phase 3 (third checkpoint): You'll want to start off with the Sai launch and drop attack then with Blade Mode cut her staff, by doing this quick most of the time she'll just run away and stand still for a bit, whilst you can approach her and try to charge a Blades attack I advise switching to your Staff and killing a bunch of Dwarf Gekkos as that'll earn you another Ripper Mode, this time you'll want to use it with the Staff and finish her off.