Thought I might as well put in a guide of the monsters here.

Well , I won't bother putting in the weaknesses ( At least , for most of them ) but I'll put in the general strategic courses to take in face of such monsters.

Kongou

The Kongou is one of the first major monsters you'd encounter.
Whilst there are various forms of Kongous , their weaknesses are generally at the back / tail and if your using the right element , you can deal a lot of damage to the Aragami.
It's face is susceptible to crush effects and it's arms can be broken as well.
The best course to take is to focus on it's HIND legs. After a while , it ought to topple onto the ground and that is the time to use whatever attacks you have in your sleeves at it's weak points.
Repeat the process and the battle would be a walk in the park,

As for the Kongou's attacks , it can be easily predicted judging from it's movement patterns so your not likely to be hitted if your careful enough.

Gboro-Gboro

A Gboro-Gboro is yet another early creature you have to face,
Whilst there are various elemental variations , the way to deal with them is pretty much the same.
Hitting the large fins on it's side is the equivalant of hitting it's legs - which would pretty much cause it to topple.
A Gboro-Gboro's fin ( The one on the head ) is easily breakable and is also it's weakest point.

A Gboro-Gboro is easily to deal with but if they come along with ANOTHER monster , it may mean trouble.
It is to be noted that whenever the top fin is lifted up , you OUGHT to hide behind the monster. However , it is also capable of performing an attack which can hit the player wherever he / she is. If a swirl of cloud appears beneath your feet , DODGE IMMEDIATELY.
Later variants of Gboro-Gboro are a bit more tricky than the earlier versions but , by right , you ought to win if your using the right elemental weapons.

3. Chi-You / Sehkmet/ Hera

A Chi-You is a fairly tricky figure.
It's lower body is fully armored and is not easy to damage. However , the wings / arms and the torso / head is susceptible to damage.
If your using high-crush value bullets , you may want to try damaging it's lower body.
Pierce is recommeded for the top half.
If your using Sunder weapons , just charge in and hack at the wings.

It is recommeded to stay BEHIND the Chi-You at all times since it have some pretty tricky moves if your facing it directly at the front. ( Particularly from a distance )
However , note that a Sekhmet ( Advanced version of Chi-You ) is capable of performing a 360 degrees attack. However , it is not flawless. Wind will burst forth from the ground in the shape of a cross , so you'd just have to find an opening between the attack.
Still , the general advice is , stay behind it , use quick attacks and hurt it real bad when it stumbles - which isn't difficult if your aiming for the head with powerful blows.

The Sehkmet is weak to Freeze weapons.

Borg Camlann

A Borg Camlann is a bit of a pain in the arse.
It's defence value is incredibly high and melee weapons of no elemental advantage is not going to work well on this beast.
The weaknesses are it's tail and with piercing rounds , the head.
Status ailments may prove necessary to this battle.
Note that you can cause the Aragami to topple by focusing on it's legs and the shield can be broken to incur more damage into the Aragami.

The general idea of fighting a Borg Camlann is - be alert.
It is dangeous regardless of your position - though more specifically the front.
You may want to check out what your allies are doing when fighting this creature.
It is to be noted that when this Aragami starts to shield itself , you may want to move out of it's potential range. If your allies are still rushing in to attack , just stick to the back and whack it hard.
If your allies are RETREATING , however , mimick them are run off - if it's too late , use your shield to block the tail swipe.
If you can do a double jump , use it to dodge the swipe.

5. Susano'o

A Susano'o have the same base moves as a Borg Camlann but it have a few aces up it's sleeves... or spikes.
It's 360 degrees tail swipe move have a longer range and it will leave elemental orbs behind it's trail.
A Susano'o's weakness is the SPIKE of it's tail. You can hit it when the Susano'o is enraged and got it's tail caught up in one of it's attacks or by knocking it down by hitting it's legs.

A Susano'o is very dangerous to confront by the front - so it's recommeded to stick by it's bum like a dirty old lecher.
However , remember that it's TAIL can still give you quite the whacking if your not alert enough and the Susano'o is fairly quick in it's own right.

Otherwise , some good ol' Divine weapons could give you quite the edge in this battle.

6. Vajra / Prithi Matva / Dyaus Pita ( The Emperor )

A Vajra is a powerful enemy - early on in the game anyway.
It's "cape" is highly durable but once broken , the battle would become easier as a whole.
The face and the tail is highly susceptible to damage.
If it sustains enough damage , it may stumble for a moment , allowing you to dish some extra attacks.

The Vajra is quick and nimble. If it starts running towards you , dodge the moment it pounces.
It is also capable of charging several electric balls - which would be shot out in a 120 degrees manner.
You can take advantage of this by moving to it's side and Devour it with this opportunity.
When angered , it's pounces may occasionally come along with a large burst of electricity so dodge well.

Prithi Matva shares a similar moveset and it is also fairly aggressive. It's defences doesn't seem to be quite so impressive but as they say - the best defence is the best offence.
The Prithi Matva have some pretty impressive hit area value attacks and when it flips overhead , dodge as the landing would incur a 360 degrees attack.
It's large area attacks can be quite a pain so the act of "hit-and-run" is important for this battle.

The Emperor , or the Dyaus Pita , is truly a pain to fight against.
It shares similar movesets to a Vajra and a Prithi Matva and it's defences is admirable.
Breaking it's cape with powerful attacks ought to be your priority as it would make the ensuing battle go along an easier course.

Sariel / Fallen Sariel / Aethus / Zeus

All of them have similar movesets so I might as well lump them together.

Essentially , the Sariel variants have powerful homing attacks so it's best to stick close to them.
However , it does have a fair bit of lagtime prior and after each attack so despite it's "mobility" , there are many chances to deal some damage.
The top of it's body is weak against attacks - though the legs are susceptible to damage as well. Though the thing is , the legs are covered by hardy skirt armor and can't be easily reached.

Oddly enough , if you go for the legs , it will fall onto the ground and be renderred helpless against any attack you would have to offer.
So going for the legs isn't a stupid decision at all - as it would make the torso exposed to an assortment of attacks.

However , sticking close to it isn't 100% safe as later variants of the Sariel can emit poisonous pools of toxin beneath it and when it spreads it's wings , a large beam of light will spread around it.
Though you can also make use of this beam of light as it only have a "hit once" effect. If you block the beam , you can rush in to have some free hits on the Sariel - or stay afar and send in some shots whilst it is immobile.

Ouroborus / Fallen Ouroborus / Amaterasu

The Ouroborus variants are big , slow but can give you quite a whacking.
The Ouroborus' defences are pretty much above average - save for the head and the limbs when it is enraged.
The Fallen Ouroborus is the same as the Ouroborus - but it's AI is improved and it's generally more aggressive , but it is also a mite bit slower.

The general tactic of fighting against an Ouroborus is - devour as much as possible. It's not difficult owing to it's size and speed and you can easily feast on it's oversized hinds. ( ... Sounds pretty wrong )
Then pass the AA bullet to your allies and watch the fireworks.

The Amaterasu , however , is different. ( Not only in appearances , but also defence values )
Other than it's suggestive and distractive meat sacks which hangs loosely off it's chest which shakes at every move ( Lord , is this game seriously rated Teen? ) , it is also A LOT more powerful than a common Ouroborus.
An Amaterasu shares similar move sets to an Ouroborus , but with slightly more ranged attacks and aces up it's... ehh... hide?

Ranged attacks aren't all too effective against an Amaterasu so you might want to bring a squad of melee combatants - favourably Newtypes for AA Bullets as they are critical for your battle.
Amaterasu Aragamis are pretty slow but if you got caught up in one of it's attacks , expect a good chunk of your HP to disappear from the bar.

The battle is going to be long as bullets aren't effective against it and it's defence value is pretty migh as well.
Essentially , stick to it's back and run like there's no tomorrow the moment it leaps into the air or sends it's tentacles into the ground.

Otherwise , a battle against an Amaterasu is mainly about stamina - it's not actually that difficult as people had said ( Just carry enough recovery items and some reliable teammates ) but remember that it does get a bit faster when it's enraged and you'd definitely die if you don't dodge when it starts attacking.
Like with the Ouroborus - stick to it's back - to the front when it stumbles.

Quadriga / Tezcalipoca / Poseidon

A Quadriga isn't all to difficult of a foe - if you have the right tools.
Elemental prowess and bullet prowess is key to victory.
A Quadriga's missle pods , head and chest is extremely weak against attacks so you might want to aim for those spots.
Hitting it's FRONT legs will cause it to fall to it's knees... or legs.. or whatever you call those.

When it falls , you may want to decide between Devouring or using a chain of powerful attacks to it's exposed chest.

However , a Quadriga's attack can be difficult to dodge owing to it's size and offensive nature. The homing missles needs to be dodged at the RIGHT time and it have a large attack radius as a whole.
360 degrees attacks are common with this foe so you might as well stick to it's front - just remember to dodge when it starts nudging about.

The Tez ( I'll call it that for convenience ) have similar movesets , but it is... say... a lot more annoying.
It is capable of using unexpected moves at unexpected times , like dropping a bomb over your head.
Dodging often is key to this battle - though you don't really need to worry that much if it isn't facing you.

Arda Nova

A pretty annoying duo - but the idea is - stick behind it's back like just any other Aragami.
Your focus should be the "God" ( The gigantic tankard that floats behind the "Goddess" ) and the Goddess should be saved for later.

The God Arda Nova is capalbe of using a variety of ranged attacks - but most of them are shot through the front so stick behind it and whack it hard.
Since it's afloat in the air , jumping is necessary but take note of the Goddess' movement before doing such a reckless act. The Goddess is capable of doing 360 degrees attack , such as swiping you off with it's limbs or summoning a gigantic tower of light which surrounds it to blast you off your feet.

Fortunately , the God is less durable and is likely to fall quickly if you focus enough attacks upon it.
Then , you can focus on the Goddess.

Whilst it may be alone , it can still dish out some pretty powerful attacks. Aim for the halo on it's head - that is it's weakness.
When fighting against a lone Goddess , the idea is - hit it a few times , leap back , see what it does and go back in.
You DO NOT want to be caught in those attacks.

This is Work In Progress - I'll try to finish it up with as much details as possible. Such as breakable parts , vulnerabilities , Pierce / Sunder / Crush weakness , part vulnerability and stuff like that.