You need at least 45 entropy effects active to unlock full bonus rating.
50-53 is the sweet spot. Anything above 53 is just extra pain for no real reward.

Here’s the exact list I use (50). Almost all of these are easy to deal with or ignorable:

🟥 Standard enemies deal more damage: MAX
🟥 Traps deal more damage: MAX
🟥 Elite enemies summon: MAX
⏱️ 6-minute time limit: ON
💔 HP Recovery Rate: -50 (Avoid 100% its painful)

📦 Exchange Space – 4 items hidden: MAX
🔧 Selecting Potentials: MAX
🔥 Advanced Battle Space Difficulty: MAX

This combo gives you basically all the rating bonuses with minimal actual gameplay penalty. If you're looking to just finish this cleanly and without rage, this setup is the way.

You cant use the "Hide choices" Entropy. It will make your life miserable trying to tweak your character correctly.

MIND CRYSTALS

Mind Crystals won't make or break you, here's general advice.

+Attack, +Skill, +Dmg on Debuffs, +Dmg on Elites, +Dmg on Fresh enemies.
You can use +Dmg on Combo, +Dmg on Kill it's not set in stone.
Avoid garbage crystals like +AP, Heal on next room, etc.

Pick the character you want to push to 4000 rating.
Pick a good color. This is very important. It's saved with your character at the end.
Pick two good legacies.
Load into Mind Training with the setup above.

Your job is to Perfect Clear every room in Area 1.
Yes, every room.
Yes, including the boss.

If you get hit at any point, exit and reload the game immediately.
You want a clean run with full Perfect Clear rating from the start.

At the start of Area 2, check the choices.
If Black Market is not there, abort and restart the run. Sorry.

Inside the Black Market, look for:
"+50% Max HP for every Perfect Clear"

If it’s not there:
↪️ Reroll once
❌ Still missing? Abort and restart. Again, sorry.

This bonus is critical. It turns each Perfect Clear into a snowballing health boost. You’ll be basically unkillable by the end.

This is the core exploit that makes the whole method work:

📌 The game only saves your progress at the start of the floor.
It does not save during each room until you finish.

If you get hit in a room:
🛑 Quit the game (Main menu)
🔁 Reload and try again (Continue)

There’s zero penalty for this. You can retry rooms infinitely until you get them perfect.

I usually end up with all perfects except Bite, Oread, Susanoo and Reki. Mostly because they're not worth the trouble for the score.

Every successful clear gives:
✅ Full rating score
✅ +50% Max HP (if Black Market buff is active)

By the end, you’ll have somewhere between 15,000 and 25,000 HP, depending on your EVO setup.

This isn’t cheating, it’s just how the save system works. You still need to be good enough to survive cleanly and to make the best combo and kill chain possible.

To hit 4000, you want as many battle rooms as possible. The more fights, the higher your score.

In order of priority:

🥇 Advanced Battles
🥈 Potential Rooms
🥉 Tactics Rooms (Pick highest quality even if you don't like the ability for max score)
💖 Exchange Points / MAX HP / MAX MP
🪙 Trial (Sometimes) / Exchange (If forced)
❌ Rest / Sortitio / Covenant

🟨 Avoid filler and shop rooms unless you’re overflowing with points or Rest is the only alternative. In Exchange rooms, pick the choices 3-4-5, then refresh, then 3-4-5 and exit. Always. You need around 800 points for each Exchange room to maximize correctly.

✔️ If you've been Perfect Clearing and stacking HP, you should have 20,000+ HP by the end.
You basically can't fail unless you fall asleep, but you'll need your A-game to Perfect Susanoo.

🔥 BONUS CALL-OUT: PERFECT REKI
Going for absolute best score way above 4000+? You’ll need Perfect Reki.
GOOD LUCK.

Avoid the following at all costs:

❌ HP-draining skills or passives
❌ Abilities that burn HP over time
❌ EVOs like Ragna that lower HP or make it unstable

None of these break Perfect Clear by themselves — but they make it impossible to track if you got hit or not. And that’ll mess up your 50% HP stacks without warning. Ending a room with just "CLEAR" because you got a 5 damage tick is not good enough.

You want total control over your health bar visibility.

If you want to max Ragna, you'll have to either be religious about checking if you got hit, or stop using his skills. And avoid the HP damage potential.

🧪 OPTIONAL BUFFS THAT HELP
🛡️ Trial: No Damage on First Hit
Gives you a grace hit. Saves runs. Easy pick. You do lose a combat room however.

🌀 ICEY Legacy
Blue Bubble = free hit.
BUT the confusion debuff is miserable. Avoid unless you’re really confident.

🌫️ Light Tactics
Makes enemies blind. If you’re not confident in your dodge timing, this will become your best friend.

I also strongly suggest you keep the Dodge Slowdown option in the menu ON, and if not use Jin's legacy power for Slow.

✔️ Perfect everything, including Susanoo and Reki = 4000+
❌ Only miss the 4 harder perfect bosses = around 3800-3900

3900 is still valid unless you're a score purist. You only need 4000 if you're trying to flex or OCD round numbers.

🐉 FINAL THOUGHTS
This is the cleanest, least painful way to hit 4000 rating:

✅ Abuse the HP stacking Black Market bonus
✅ Abuse the save system for Perfect Clears
✅ Abuse your own patience
❌ Don’t abuse yourself with entropy picks that actually suck
❌ Avoid becoming insane and only perfect the bosses from Area 1-4 and inside the Space, not Susanoo and Reki.

Once you hit 4000, your EVO can handle Boss Parade solo mode. People will ask why your bar is 3.5 times the width of your TV.
Take your win, collect your rewards, and tell everyone you did it first try.

💬 Questions? Probably not. Report to the devs? Yes, this is broken.

Credit to ChatGPT for formatting, the entire contents are 100% mine.