As usual, feel free to discuss any of the points I've made, and make suggestions if you feel like something's off.
[Overview, Weaknesses and Strengths]
Odachi is one of those weapons that looks amazing, but for some odd reason, very few higher levels play. Like the other two power weapons, its a weapon that is heavily cash reliant. I would like to note that, in addition to this, it's also one of the more frustrating weapons to gear, and requires more thought than the other two. By extension, this implies that good gear is also more difficult to obtain. This is due to how spread out Odachi's elemental multipliers are.
In addition to this, Odachi suffers from a slightly below average attack speed. Although it has the second highest maximum attack, it's attack stat is rather spread out, leading for the effective weapon attack to rank third, with Axe and TS taking the first and second places respectively.
Don't be deceived by my wording. While I call it a big sword, Odachi and sword are two completely different weapons that have completely different playstyles. Odachi has a slightly higher average attack stat, but, unlike sword, it is relatively immobile. Despite the fact that they share many basic skills, Odachi skills tend to have better damage distribution in mobs and slightly worse cast times. In other words, Odachi is able to deal with mobs more easily. As a result, they are the only power based weapon without a heavy early game ougi reliance.
Note that mobbing becomes less of an issue in Edo, leading Odachi to fall off slightly. However, that doesn't mean that Odachi is not viable in the Edo content cap. Seeing as how their main element is holy, Odachi is one of the best Satan-killing weapons. Compared to Axes, Odachi also has significantly better SP sustain. This is both due to the nature of their skills, as well as the build path Odachi follows in order to maximize its damage. Though lacking the sheer damage numbers to shred monsters with ease, they can still mow through mobs with their spells.
tl;dr: If you want decent damage, good mob potential, self sustain, and don't mind rolling/spending for the gear you need, Odachi may be one of the choices you should consider.
[Skills]
In this section, every skill will be ranked S - F, and some other details will be provided. Analysis may be included if I feel that the skill is worth it. Note that multi-click skills tend to have better scaling, but this does not imply that they do better overall damage.
Blazing Swing
Rank: C
It's similar to axe's blazing swing, with a bit more length in the range. However, the problem still holds, that is, it has difficulty hitting enemies that you jump on directly. The problem feels less prominent than with axe, but it's still not great.
Collapsing Blade
Rank: E
Good damage output, but not viable due to dura nerf on NA.
Empty Sky Slash
Rank: B/S
At lower ranks, this skill is not very good, hence the B rank. However, once you hit rank 6, it takes a sudden damage spike, and starts doing much more than it ever had before. It's very powerful, and scales well with your build once it acquires its holy element. Its slashes are fast, and can be cancelled at any time. This is probably the most important skills for clearing dungeons in Edo.
Dust Storm Blast
Rank: B
You can bait mobs of monsters into this skill, and then kill them. It has a pretty large hit limit, so its very good around Kaga.
Fierce Slash
Rank: C
While this skill is alright at lower ranks, it becomes very mediocre at higher ranks. At rank 6 or 7, it suddenly changes from a single swing attack to a double swing attack. The total damage increases, but the damage is split into two swings that force awkward movement.
Grim/Sacred Strike
Rank: A
One of the best skills, while its speed isn't the best, it does very high damage due to your build. Note that there is a disadvantage to this skill, in the sense that its hitbox is inferior to it's mob limit. That is, although you can theoretically hit a large number of monsters with this skill, it generally does not happen because the slash is too small.
Icicle Massacre
Rank: C
Slower, weaker ice blossom.
Leaping/Flying Lightning Strike
Rank: C
Too weak due to capping at rank 5. Also startup delay is long.
Sacrifice
Rank: B (or F if not using Chiami)
Underrated. Although this skill's hitbox is thin, and it has some start up, most of the start up can be cancelled with the use of a tsubame gaeshi. It's damage is nice, and if you run a chiami, you can heal back the damage dealt. However, not running Chiami renders this skill rather useless.
Sword of Avidya
Rank: B
This skill is very very good at lower levels. Unfortunately, it's maxed at rank 4. While building around it is not actually viable, it was still a very good skill.
Tsubame Gaeshi
Rank: A
Fast, deadly, but small hit box. Very good for cancelling into other skills.
Void Slash
Rank: D
No point using this. It's weak and caps at rank 5.
Way of the Odachi
Rank: F
Useless, unless you don't have max affinity.
Crimson Flame Blast Smash
Rank: A
Although this doesn't fit into most builds due to the fact that it's not holy, you can still choose to run one of these. It does high damage, and has its skill force scaled differently than sword. Note that using the skill against a wall causes all of them to detonate immediately. Firing this skill from a high elevation onto a lower elevation may cause the explosions to be delayed, and travel further.
Dark Tornado
Rank: F
Junk. Low damage, weird jump that always misses, waste of an ougi slot.
Festering Violet Strike
Rank: A
The only mobility skill. Even when extracted from a Satan weapon, it's still decently strong, and helps you get where you need to get faster. If the rank 6 is used, you can definitely rely on it.
Shining Enma Slash
Rank: A
Asura spin for odachi. It's slower, and consists of two hits. Like the non-bootleg version, its very, very strong, and serves to do excellent dps. Note that the reason this is not ranked S is because holy empty sky slash has higher DPS.
Sun Searing Flame
Rank: C
Although its slow, it does a good amount of damage. Note that it's not very viable to clear mobs with, but is decent against bosses.
[Clearing Dungeons With Odachi]
Run around and slice stuff. Approach ranged monsters with Satan Ougi if you have trouble normally. If Satan ougi is down, run in a clockwise motion. Pretty easy, self explanatory playstyle.
Don't forget to mob at early levels, as Odachi is very strong in that aspect.
[Amplifying Damage with Odachi]
Unlike many other weapons, Odachi is one of the few that has only one real viable build path: Holy/Slice. While other paths can be considered, this is by far the most powerful, and the only one that allows Odachi to stay completely viable in the current end-game meta. Although Odachi might not have the best base damage, the sheer amount of obtainable multipliers throws this out the window.
Players will want to focus on the usage of Dusk Magatama. These Magatama allow for damage multipliers to Shining Enma Slash while still retaining as much power as possible with other skills. Specifically, two of those three other skills should be Holy Empty Sky Slash and Sacred Strike. The last slot should idealy be Spirit Empty Sky Slash, but players may opt to sub this out for another skill because of how difficult it is to obtain both the rank 6 and 7 versions of empty sky slash on a single weapon. As a result, the best idea is to use Tsubame Gaeshi because its fast and provides the player with a decent amount of power.
Odachi players should always take the title "Shoutoku Taishi." Note that you might need a status reset to get this title, as the requirements force you to take a less-than-ideal build. However, the benefits are worth the double status reset. First of all, this gives you 50% Odachi affinity, which is useful, especially since you won't be using a CROSS. Secondly, it gives you 30 Holy, which only serves to boost your damage. Finally, it gives you 50% staff affinity, increasing the amount of sp healing you get from meditate. Depending on your build, this can even increase by 2-3 ticks.
Note that the weapon you will be using in the current endgame meta is the Air Cleaving Sword. It offers you a good mix of elements, pumping up your damage far more than the attack stat from a Catastrophy CROSS would.
The suggested Ornaments are 6-7 fated contractor, and the rest for heavenly shield. Since the build is a holy build, the element from heavenly shield should be Holy. Odachi affinity is always a plus as its difficult to get to 6k without the satan weapon. Ideal fated contractor ornaments have slice, critical and a mix of hp and sp.
These provide damage and surviveability, seeing as how all of Odachi's holy skills are also part slice. Do be careful, as taking additional heavenly shields provides more base damage, however, taking more fated contractors increases critical rate. You should math out your damage multiplier, assuming that criticals deal about 1.5-1.7 times damage at higher levels.
Math
So why air cleaver? Attack stat has a huge influence on the amount of damage you do, and because of affinity capping at 6k, anyone that didn't roll absolute perfect rolls on their heavenly shields (Odachi affinity + Holy Element) will be losing out on a bunch of raw power. Furthermore, the vibe-tachi has impact element, granting benefits to crimson flame blast smash.
Even taking all of this into consideration, the Satan weapon was tested to do less damage. The air cleaver simply provides way too much to pass up. That is, air cleaving sword grants the user 38 holy element, 50 slice element and 30 fire element.
In other words, a single air cleaver grants almost four perfect fated contractors worth of slice element, and one and a half perfect heavenly shields worth of holy element, then grants you some fire on the side. Furthermore, you should only have about 1000 less attack stat than a vibe user assuming that you do have perfect gear, and both of you are at +100. Is this worth it? Definately.
Unfortunately, I don't have Onigiri's damage formula, and attack does not scale damage in a linear fashion, making it pretty much impossible to calculate the theoretical difference in damage between the two weapons. On the bright side, I made sure to do field tests though, which demonstrated a significant increase in damage with the use of the air cleaving sword. And you know the best part? There's an superior version of the air cleaver in the next content cap. Hence, the section below will math out the air cleaver and show exactly why it's so strong.
Air Cleaver vs Same attack Weapon
[Crimson Flame Blast Smash] - 0.7 fire, 0.3 impact.
0.7 * 30 = 21% damage increase.
[Shining Enma Slash] 0.7 Holy, 0.3 slice
0.7 * 38 + 0.3 * 50 = 26.6 + 15 = 41.6% damage increase
Note that sacred slash and spirit/holy empty sky slash share the same damage increase.
[Tsubame Gaeshi] - 100% Slice
1 * 50 = 50% damage increase
Damage Increase from Magatama (Non-air cleaving sword)
Dusk Magatama * 4 = (.47 * 4 + 1) = 2.88 times damage.
6 Fated Contractor (13 * 6 = 78 Slice)
2 Heavenly Shields (2 * 24 = 48 Holy)
[Shining Enma Slash] 0.7 Holy, 0.3 slice
0.7 * 48 + 0.3 * 78 = 57% damage increase
1.57 * 2.88 = 452.16% damage over someone with no magatama
Note that sacred slash and spirit/holy empty sky slash share the same damage increase.
[Tsubame Gaeshi] - 100% Slice
1 * 78 = 78% damage increase
1.78 * 2.88 = 5.1264 = 512.64% damage increase over someone with no magatama
Damage Increase from Magatama (Air cleaving sword)
Dusk Magatama * 4 = (.47 * 4 + 1) = 2.88 times damage.
6 Fated Contractor (13 * 6 + 50 = 128 Slice)
2 Heavenly Shields (2 * 24 + 38 = 86 Holy)
[Crimson Flame Blast Smash] - 0.7 fire, 0.3 impact.
0.7 * 30 = 21% damage increase.
1.21 * 2.88 = 3.4848 times damage compared to someone with no Magatama
[Shining Enma Slash] 0.7 Holy, 0.3 slice
0.7 * 86 + 0.3 * 128 = 98.6% damage increase
1.986 * 2.88 = 5.71968 = 571.97% damage increase over someone with no Magatama
5.71968/4.5216 = 1.264968 = 26.5% damage increase over someone with no Air Cleaving Sword
Note that sacred slash and spirit/holy empty sky slash share the same damage increase.
[Tsubame Gaeshi] - 100% Slice
1 * 128 = 128% damage increase
2.28 * 2.88 = 6.5664 = 656.64% damage increase over someone with no magatama
6.5664/5.1264 = 1.2808989 = 28.1% damage increase over someone with no air cleaving sword.
As you can obviously tell, Air Cleaving Sword provides ridiculous damage multipliers onto the player's skills. Even though it is mitigated by Magatama and the multiplier is still very noteable. Note that critical was not taken into account in this case. The total amount of critical would be the same in both cases as the magatama were not swapped out at all. Overall, having 3 perfect fateds should result in a critical of around 72, meaning that the player should see a 36.28% increase in dps due to criticals, assuming critical hits do 1.5 times damage.
Status
The status build with Odachi isn't very difficult. Since you are using air cleaver, you will want to maximize the amount of damage you get from affinity, and go for the full 100 base power. After this, there should either be a 40/75 or 80 investment into mind, followed by heavy investment in dexterity. Players should optimize wisdom and dexterity, which grant 1/24ths and 1/12ths of a critical respectively, so that they can manage to squeeze out that one last critical, if possible. Consider the fact that it is alright to be slightly inefficient if it means raising your wisdom to a multiple of 10. Also, note that Odachi has the option of adding additional mind, as they have a title that also provides affinity to staves. Adding more mind allows Odachi to gain significantly higher ticks from invigorate and meditate. However, it is important to understand that mind itself has very little effect on healing, and that staff still force is required for effective amounts of healing. Mind does however, provide a separate bonus in the form of cool down reduction.
While vitality is not necessary, it is an asset that players can be free to add. NOTE THAT IT DOES NOT ADD REAR ATTACK AS NOTED IN THE GAME. THIS IS A MISTRANSLATION. Normally, I would maximize my critical (that is, stop adding points into wisdom or dex once you realize you cannot get one more critical no matter what you do), and then dump the rest into vit.
