On the subject of Stat Debuffs and such, this is just my theory on it. Also when you say Kedama, I'm guessing you mean the regular Kedama you encounter on the first couple floors and not Small Kedama. [Just noticed there were 2 on that floor and I was thinking Small Kedama, then I noticed the stronger one]
Kedama has the following resistances to debuffs.
00097380 [this+0x0198] = 10 ; - Attack
0009738D [this+0x019c] = 0
00097397 [this+0x01a0] = 10 ; - Defense
000973A4 [this+0x01a4] = 0 ;
000973AE [this+0x01a8] = 10 - Magic
000973BB [this+0x01ac] = 0
000973C5 [this+0x01b0] = 10 - Mind
000973D2 [this+0x01b4] = 0
000973DC [this+0x01b8] = 10 - Speed
000973E9 [this+0x01bc] = 0
000973F3 [this+0x01c0] = 10 - Accuracy
00097400 [this+0x01c4] = 0
0009740A [this+0x01c8] = 10 - Evasion
00097417 [this+0x01cc] = 0
As a note, I almost got confused since I followed it from the text mentioning the stats having individual defenses, however, one thing that's been noticed by others and myself is that certain stats tend to get debuffed a lot more compared to others, so each stat having its own debuff resistance isn't a surprise. On realization, I realized the line with DBF was probably for Attack, with the last one being Evasion. As such this could mean the the Rating for it in the Beastiary is just based off the Total of all stat debuff resistances combined. On another note, this is for enemies only, not party members, who I'm guessing have the same Individual Stat Debuff Resistance as the Debuff Resistance Stat (I.E 50 Debuff Resistance = 50 to all stats)
Now for the numbers part. The 10 is pretty much similar to having a 10 on the Resistance stat itself. Since there's 8 stats, that's a total of 80, which is...well low, but it's not the lowest since it's a Red X, not Dark Red. While I want to compare that number with the Elemental Affinities, I don't think that would be accurate since I'd need a bit more numbers, mainly from enemies with Dark Red X, Triangle, Circle, Double Circle, and Star Affinities, and even Resistances as well. I'm not sure if the 0 after means anything, but I'm tempted to say it's how much that stat and such is altered, though this makes little sense due to Elemental Affinities also having it without any method of lowering, so I'm guessing I'm just overthinking it and it means nothing.
With that said, I remember someone mentioning how an enemy had a Resistance to something, not sure what, that capped out at 1000. If we use this with Stat Debuffs, then it would probably be something like 125 for each stat (125 * 8 = 1000), meaning the 10 is a 10% Chance to resist that Stat reduction. So why 125? Reisen's Intense Vertigo skill. While that number totaling at -25 for the skill is probably insane, it would make sense as a means to prevent certain stats from being debuffed. This could also apply to skills that increase chances of inflicting other ailments as well. Just another theory until actual numbers are found. I could also be wrong in that it's not subtracted from but lowers it by a %, due to what I mentioned at the start about a Resistance capping at 1000. On the other hand, the 1000 could just easily be a method for the Devs to say "No, you're not inflicting this on boss, at all".
Ok so now let's look at the Party Members. I'll only look at Kasen since it's the easiest one for me to find. Using the formula for Kasen's Higekiri's Cursed Arm, we have these numbers
Higekiri's Cursed Arm
- ((ATK 165%) - (DEF 50%)) * (1.60 + 0.05 * Lv)
- TRR power = 16000
- TRR chance = 100
- ATK Debuff = -18
- ATK chance = 100
- SPD Debuff = -18
- SPD chance = 100
Ok, so Chance = 100 would probably mean it's, by default, a 100% chance of inflicting it with 0 Resistance. Now let's look at the Kendama's resistances for Terror, Attack Debuffs, and Speed Debuffs.
Kedama
0009733B [this+0x0180] = 10 ; - Terror
00097348 [this+0x0184] = 0
00097380 [this+0x0198] = 10 ; - Attack
0009738D [this+0x019c] = 0
000973DC [this+0x01b8] = 10 - Speed
000973E9 [this+0x01bc] = 0
Using those 10s, we subtract that from the chance, so now it's a 90% Chance for each effect to activate. But there's another thing we need to look at, and for HCA, that's TRR power. Now I'm not entirely sure about this one, especially since....well..
Ok so I hacked Kasen's stats so they're at 1 Attack so she can't kill the Kedama. With HCA, I was able to inflict Terror. With Kasen at 10,000 Speed and a party member having 9999 so they'd go directly after, I was able to get 2 different results from the Terror Power upon inflicting.
Kedama 1: 15392 Terror
Kedama 2: 14592 Terror
So similar to dealing damage, there's some RNG being thrown in to alter the final output. To note, I tested a few more times and never hit 16000. At the same time however, I hit a Great Tree's Enormous Wasp with Terror, and the number was 17600. When comparing it's Terror resistance, it was a Dark Red X, compared to the Kedama, which was just a normal Red X. This makes sense though.
But now this kinda questions my earlier theory about the Resistance levels. It could just be Stat Debuffs use a different method to determine it
I also feel that Elemental Affinities use a different method to determine it's ranking.
Looking through the Elemental Affinities, Fire and Dark are 66 and everything else is at 100. On the Beastiary page, the enemy is Neutral to those 6 elements but Fire and Dark are a Red X. Using my current Beastiary and checking all the Elemental Affinities, I've found only 2 enemies with a Dark Red X, and they're both from Post Game (Emerald Nut and Green Ooze, both with a Fire Weakness). Considering 100 is Neutral, and the Kendama's 66 for Fire and Dark is just a Red X, I'd probably say that Dark Red X, Red X, Red Triangle, and Neutral are around the following values.
0-49 = Dark Red X
50-74 = Red X
75-99 = Triangle
100 = Neutral
Obviously without any numbers just yet for Circle, Double Circle, and Star, I can't compare those properly.
Again, this is all just theorizing. Once more numbers show up and such, maybe we can figure it out more.