1) Gauntlet Hades is ridiculously powerful for a 1st level maneuver. Compare to the other 1st level Soul Eater maneuver Life Draining Swipe (which is appropriately powered, btw) to see why. This thing just does it all! A chance for two attacks, maybe some self healing, and knockdown (maybe two shots at it)! WAY too good. Thankfully, this was the only maneuver that was OMGWTF here.
Would pushing it to 2nd level solve it? Since Hell's fang is similar and you didn't mention it...
2) Infernal Divider already knocks fools prone if you hit, so when Infernal Drop Kick knocks them prone again it does nothing. I'd suggest replacing the second iteration of prone with something more relevant. Maybe they lose their next move action (aka they get knocked prone hard)?
Considering this action denial route: using the effect you proposed, the guy would still spend his standard action and get up, or attack while prone (taking -4 to hit). What if it stunned the target for 1 round instead?
3) Infernal Push, pushes fools, but I'm a bit hazy on how you want it to work. Divider knocks them ten feet into the air, and then you use Push. Did you mean for Push to knock them higher into the air or just throw them 10ft horizontally?
Yeah.... it was meant to push them horizontally...
Fixed.
4) Death Spike's reminder text is somewhat misleading. The way it's written could make some newbies think that, for each creature in the area, you heal 2d6/creature. Which is a lot of healing, and surely not what you meant.
Hum.... What would you say if I said "that was exactly what I meant"?

Reducing it to 1d6 per creature might look nice if hitting 4 targets, but not so hot against a single target... Maybe start with 2d6 and increase to 1d6 per additional creature affected?
5) Death's Grasp is underpowered in my opinion. It has the advantage over Dancing Blade Form of adding to your reach even when it isn't your turn, but DBF always seemed underpowered to me as well and it's 1 level lower.

What do you think of putting Death's Grasp at level 4 or 5? Can merely lowering the level solve the problem?
6) Belial's Edge II could use a little extra love. It's pretty boring and a smidge underpowered to just deal 12d6 extra damage at 13th level. Maybe add a save or be shaken effect?
Sadly, Belial's Edge have no other secondary effect. Ingame, it is used to lenghten Ragna's combos, while dealing some damage. Besides, fear effects at 13th level are not very effective anymore...
...I guess increasing the damage won't cut it, right?

7) Black Onslaught has a lot going on and could maybe use powering down just slightly. Also, it appears to target just one creature, but sometimes the wording makes me wonder if I can full attack and spread my attacks and cause lots of creatures to save or die. Which, honestly, could be pretty cool, but then the maneuver would need a big overhaul.
Fixed text to affect a single target.
1) Delayed Strike is going to stress DMs out. Most DMs I know think that Mountain Hammer is already too powerful and this, for the price of a full round action, is more accurate and deals more than double the damage. I would rethink this, possibly making it ready an attack, possibly making the initiation 1 entire round, I'm not sure. The answer here is difficult, because Mountain Hammer is already powerful enough and already uses the flavor of one powerful strike, which God Slash is built around.
Hmm... I never heard about Mountain hammer being overpowered (aside from it cutting through adamantine like a hot knife would cut a piece of butter)...
Would it help if the bonus to hit was removed, and the damage decreased to 3d8 (or even 2d8... but I would be very sad

)?
2) Horizontal Stab, having a silly name notwithstanding, mentions that it can be used as an attack of opportunity. Technically, you won't be able to benefit from the extra reach of the strike when you use it as an attack of opportunity, something you may have already known, but most players would not know this and it would become a confusing headache in play. Again, I'm not sure what the best solution here is.
Laugh as mush as you want, but the name describes it exactly how it is... a stab with a bigass sword...
What if I add the following to the end of the maneuver: "Additionally, if a creature moves within 15 ft. from you, you may use this maneuver as an attack of opportunity against that creature."
3) No Escape seems underpowered. Spend an immediate action for an extra 5ft step and only when a foe provokes an AoO? I don't think I'd ever go for this. Might work as a stance where you get a free 5ft step whenever you make an AoO?
Thinking about it....
4) I can't decide if I think that Enma is overpowered or that Hotaru is underpowered. Honestly, I'm starting to think it's a combination of both. I think if you modified Enma so that it was a normal Bull Rush attempt with an automatic 10ft push on top but you lose the knocked prone part that would work for Enma, and if you just gave Hotaru +2d6 damage that would work there.
Removed the knock prone from Enma, and added 2d8 extra damage to Hotaru.
5) Cut Magic seems a little unclear and a little overpowered. It says you can counterspell stuff within 30ft, but it doesn't specify how this works. I assume you mean that the initiator can ready actions to make Sense Motive checks which in turn mimic
Greater Dispel Magic, but I'm only able to assume that because (not to toot my own horn) I know so much about how the game works.
My suggestions here would be, first, to lose the evasion part, and second to allow the initiator to ready actions to counterspell (as described
here) only against spells cast within his threatened area or targeting creatures within his threatened area.
What about this?
[quote author = Cut Magic]Whenever you hit with a melee attack while in this stance, you may attempt to dispel magical effects on the target. Make a Sense Motive check at a -10 penalty in place of a dispel check. This otherwise function as the targeted version of
greater dispel magic. Additionally, you may use an immediate action to counterspell a spell cast by a creature within your reach or affecting one or more creatures within your reach (including yourself) as if using a
greater dispel magic against the spell. [/quote]
6) Zantetsu is another example of taking a maneuver that most DMs see as overpowered and turning it up to 11! In Devoted Spirit we have the Divine Surge maneuver at 4th level which is a single strike that deals +8d8 damage and everyone I know thinks that's too strong anyway.
I never actually met someone who thought like that... must be because I know so few DMs

By comparison, even against a creature with DR 10/--, assuming Crusaders with Greatswords and Str 22, Divine Surge deals an average of 42 damage after DR while Zantetsu will deal an average of 57 damage after DR a pretty sizable difference which can only increase against less protected targets.
Lowering the damage to 4d8 per hit is enough, or it's still overpowered?
7) Tsubaki, again, just deals a bit too much damage. With the potential trip attempt, with bonus, something as small as 6d6 would suffice.
Reduced Tsubaki's bonus damage to 6d8...
8) Kokuujin Ougi: Mugen is completely over the top and actually WAY better than the 9th level maneuver. Due to how it's worded, I don't think you meant for it to work this way, but you can just spam the same manevuer twice. So Zantetsu(x2) for four attacks and 20d8 extra damage to kill just about anything with standard action, or simply unleash a double strength Kokuujin: Shippuu for 26d8 area effect damage. It's a bit less than Zantetsu, but you will reliably deal the damage and to a few targets at once. The "not expended" clause is just moar power on an already too-powerful effect.
I don't think there is a solution to this one, other than scrapping it. If it allowed two standard action strikes as a full-round action, and if they were expended as normal, it might be okay.
Sadly, that's exactly how it works ingame. Maybe putting a level limit.... like only maneuvers from 5th level or lower? And/Or maybe making the initiation time of both maneuvers a full round action (without expending them)?
@the 9th maneuver: you think it's weak? Maybe adding some extra damage on each attack?