This trophy is obtained by defeating Monsoon without taking any damage on Hard difficulty or above.
If you are like me and seriously lack the qualities of some individuals that seem to burn through this game on Revengeance difficulty obtaining that Stormbringer trophy while half asleep as though it is no big deal whatsoever, let me just say this:
You can do this.
I will repeat:
You can do this.
That was your first round of encouragement in this motivational sandwich, however the second round is the reality check: Monsoon is a cheap, unpredictable, speedy bastard (did I mention cheap?

). He will rarely do the same thing twice, and just when you think you got his patterns down, that asshat will go and throw something new in the mix. You will cuss, you will hit stuff, hell, you may even shed a tear (as I did

), however I am here to lend some advice on this battle. I will just say this one more time to complete the motivational sandwich:
You can do this.
WHAT YOU WILL NEED TO BEAT MONSOON DAMAGE FREE:
1. A backup save (and, honestly, get that practice in now - you will need it for Stormbringer).
2. A complete understanding and damn near expert use of the parry system
3. The Sai or EMP grenades (you can get those during the battle though)
4. Patience
WHAT WILL ASSIST YOU IN BEATING MONSOON DAMAGE FREE (however not necessary):
1. A maxed Muramasa blade
2. Infinite Wig A (if you go the EMP route)
3. A maxed Pincer Blades
4. Custom Body Red
So, lets get down to the meat and potatoes of this battle: Monsoon between 100% and 70% is the most dangerous. Plain and simple. this is the first few moments of the battle.
Why is he the most dangerous then? Because that is when he is the most unpredictable. He has an array of maneuvers, some that take him off-screen, some that have him moving faster than you may be able to keep up with at first. He is fast, he is a combo beast, and if you think taking him head on is a good idea, think again.
At this point I am assuming you are aware enough of the story to have the following equipped IF you have them unlocked:
Muramasa blade (and hopefully it is maxed)
Custom Body Red
Infinite Wig A
If you don't have the latter 2, it is not the end of the world. If, at any time, Monsoon lands a hit on you, hit Start and select the "Restart" option - you will start the battle over again, and that damage will be removed from the record. At first this seems awesome, however as the battle rages on, and you get him close to done, and screw up royally, it will be frustrating as all hell

. Now, back to Monsoon, and how he will try to hit you from the jump.
STAGE 1- Monsoon 100% to 70% health: At the start of the battle, Monsoon will be gunning for your throat. You have two options here: Ninja Run to the left, or Ninja run to the right. Forward is not an option. Period. Remember that. DO NOT RUN AT HIM. Make that bastard chase you. You want him to do one move: his jump-30-feet-in-the-air-and-dive-bomb-the-crap-out-of-you. This is where you need focus, and an excellent understanding of the parry system.
As he comes down, you want to defend, but don't do the "perfect parry" that counters - it will knock him away. You want him to hit the ground near you as to gain a few seconds where you can deal a good 5 to 10% health reduction on the bastard. That is where you want the direction of this first stage to go, however, we all know jerks, such as Monsoon, rarely do as we would like.

Monsoon will also try to give you a roundhouse, where you can easily run away from, however it is a good idea to circle back and get in a hit or two.
Monsoon will also try a devastating combo that will push your limits regarding the parry system. You will know what he is up to as his sai's will turn purple and he will be trying to jab you.
Monsoon will also try to launch you in the air - if he is successful, restart from the checkpoint.
Monsoon will also throw some red phosphorous grenades down and try to attack you from several angles. I have read other guides that stated "If Monsoon does that, restart immediately". I don't know why, but I never had a problem with him doing that. Just be careful if you wait that move out - sometimes his last attack will also be that nasty devastating combo above. Also, do not be near Monsoon if he sets off those grenades - for some reason they take away health, so you will have to restart anyway.
So, in Stage 1, the attack you want him to do is the one from the air. Keep running from him in the beginning, and get some distance - more often than not, he will jump up to attack. Then do the non-perfect parry, and cut him up

.
STAGE 2 - Monsoon 70% to 40% health: Congratulations - the most annoyingly hard part is over. Monsoon will be taking the high ground, and give you a moment to take a breath. If you don't have it equipped, select either your Sai, or the EMP grenades.
Now, Monsoon will say a few words, then he will start throwing tanks and choppers at you. Fun stuff. If you want EMP grenades, but have none, initiate blade mode when prompted on the screen: the vehicles he throws often drop EMP's, as well as health (but you don't need that here, champ

).
If you don't want EMP's, and don't want to waste your time here, then when Monsoon takes his position, run to the opposite corner of the map. When prompted to initiate blade mode, instead Ninja Run towards Monsoon. All those vehicles will fly over your head

. This works every time, no matter how many vehicles he has in the air.
Anyway, monsoon will toss two sets of vehicles at you (Set 1 = 1 vehicle, Set 2 = 2 vehicles). Cut them up, or run from them, and then Monsoon will jump down. At this point your Sai should be purple - press the triangle button and stun him. Or, if you would rather use EMP's, use them. Either method works.
While Monsoon is stunned, run up to the bastard and blade mode his face. His head will roll away. If you have the Pincers maxed, quickly equip them here. This is crucial, and requires nearly perfect timing.
With your pincers equipped, run towards the head (but not to close - most of the time you don't even have to move from your spot

), and charge the triangle attack. Wait for Monsoon to nearly pull himself back together, be flipping back to his feet, and unleash the hell that is the pincers on his ass!

That bastard will cry out, be thrown back, and then jump back up to a corner to throw more vehicles at you. Rinse and repeat until he is at 40% health.
STAGE 3 - Monsoon 40% to 10% health: So, now Monsoon is a bit pissed off, and he is going to hurl this amalgam of vehicles spinning like a wheel at your face. Before you do anything, equip the sai - you will need it. Parry the wheel of death twice, and you will get another blade mode prompt. Do it, and cut that thing to shreds.
Then Monsoon will drop down, say something stupid, and hurl his right arm at you. You need to perfect parry that attack. I am not merely suggesting here - you
need to do it. Doing a perfect parry on his appendage will knock it down completely. Just parrying it will make you have to parry a few more times, at different intervals, leaving you open to getting hit. PERFECT PARRY HIS ARM!
Once you do that, immediately press triangle before he throws his left arm - if you have the sai selected (as you should) it will stun him. Run up, and repeat the action from Stage 2. He will jump to the corners again, throwing even more vehicles. It would be wise to run from them, as you can lose track of them during blade mode, and you really, REALLY don't want to get hit at this point.
Get him down to 10% health and the final stage will be initiated.
STAGE 4 - Monsoon is a dead man walking: So, you kicked Monsoon's ass to the point where he is throwing a second wheel of vehically death at your face. Just like before, parry twice, then cut it to bits.
Now, at this point Monsoon will start lifting a very large, and pointy, monument off to the right of the screen. When you see that, check your health - if you are still full, then congratulations: you will unlock the trophy. If not, quickly restart.
Why do I say restart? There is a checkpoint when Monsoon hurls the monument at you. If the checkpoint saves, then you will need to go to your backup file and start again. Not fun.
Anyway, complete the QTE's, hack up this awful, awful bastard and this trophy is yours. Congratulate yourself as you have just defeated one of the most annoying bosses in this game with him never laying a finger on you.

Questions, corrections and neg vote justifications below.