Writing climactic battle scenes (+ kittens)

I'm working on the climactic battle scene of my current novel, and as I was preparing for this, I realized the task was going to be complex.

Write battle. (I haven't done this before.)
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Write climax of the story. (I haven't done this before either. This is my second novel, but the first in which that I have gotten this far.)

So what do I do? I research.

There was helpful hints out there, but they were scattered all over and embedded in articles about larger story structure.  So I had to collect them and chew on them and digest them.

I'm going to share what I found. (Whether I can implement all these principles in my own novel remains to be seen, but at least I can make this helpful to you, dear reader.)

*Ahem.*

How to Write a Climactic Battle Scene

Make sure each character has a goal. Make the goals clear, and make it really matter. If the character doesn't succeed, what do they lose?  Power? Control? Freedom? Wealth? Respect? Love? Loyalty?  Life? The lives of all they love? Their soul?  Will all the fluffy kittens die and no more rainbows will appear forever?

Also, point of view will need to be carefully chosen for greatest impact at various points.
Pay attention to each main characters’ internal and external goals for the scene and for the story.

Involve suspense.  Show the preparations of Lord Evil of Mount Doom-y Doom and how they will exploit the protagonist weaknesses so that they see something terrible is coming.  When the readers know more than the characters do, it creates dramatic irony and suspense.

Make the hero vulnerable. i.e. they can be killed, trapped, enslaved, destroyed politically or professionally, or ruined financially or socially. Vulnerability can come from the character’s own physical, mental or emotional shortcomings and conflicts as well as from the machinations of the adversary.

Threaten character’s safety, goals, morals, possessions, freedom, family, beliefs...  And their kittens.

Rack up the tension and suspense by making more and bigger promises about problems to come – disasters that will devastate the hero and his allies, shatter his plans and bring him so low that he might never recover.  Climaxes are where the consequences come after the hero.
(Show the dreadful kitten-gun that will be leveled at all the kittens.)

Create effects that spread the danger and damage early in the fight. Everyone should feel they are in danger, even the antagonist.

Focus on who is the largest threat to the villain and knock out a few heroes, but avoid downing them so early that they don’t feel like they can contribute. 
Make sure the hero appears as the underdog. (Or an under-kitten?) Or reduce them to underdog status quickly. However, avoid effects that completely neutralize character abilities or arbitrarily cripple them.

Being forced to compensate for a lost ability can be a good end for a minor arc, but for the campaign’s end, the heroes should be able to use everything they've learned and everything in their arsenal.  Even their kittens. (Rarr.)

There will be moments when the characters calculate chances and risks and analyze advantages and disadvantages of various courses of action. There will also be moments when they act on instinct and go by their gut.  (Like kittens.)

Consider when you can include a shift in tactics or calling for guards, or a transformation of the environment.  Negotiation turns to violence. Violence turns to diversion (like when the herd of kittens is released into the yarn factory). Success that is shattered by an ambush from the side.  Or mix these all up.

Remember to use scene and sequel. One act leads to a response, that leads to another.
With battles, efforts to destroy are "up to 11" on a scale of 1 to 10.  No punches are pulled unless there is a chance that the opposite side is weakening and may give in. (Punches may not even be pulled then.) For the antagonist, diplomacy is battle by words, and parley and peace is delaying battle for strategic advantage.
Try to avoid a fight of attrition.

Let your hero think he’s won – then tear victory from his grasp and turn it into absolute, crushing defeat.

Up to this point, the protagonist has been contemplating a transformation. Now she’s tested to see if she has changed.
Make your hero face his/her greatest fear – and risk losing the thing that matters most to him/her. (I hear you ask, "Like maybe losing their kittens?" Yes, maybe.) 

Expose protagonist to his greatest nightmare. (Kitten zombies?) Make sure to have warring emotions at the time of greatest decision.
Then tip it to one side with a little factor of deep meaning that offers a glimmer of hope or inspiration. (like kittens!) (The little factor has to be carefully set up and invested with meaning in the previous scenes for this to work.) Alternatively, if no hope of survival can be offered, offer a glimmer of hope that a sacrifice will not be in vain.
Make the peak moment of the scene run in slow motion with excruciating detail in description. Show it through all the senses.
Includes a moment of truth  -- The protagonist must realize ______.

The impossible task. The last stand against the enemy.  The kitten's back is against the wall, cornered by the wolves.
The hero must solve their own problems in the climactic battle. (Must define what the problems at the various stages)

Climax needs to resolve love plot and adventure plot.
The climax must fulfill all the promises of the story. (So you have to keep track of all the promises you've made about what the battle will be like or what might be used and prepare a way to keep them.)
It must also answer the story question.

The climax must settle the issue of whether the hero will or won’t achieve the goal.
1) The hero achieves the goal. Happiness ensues. Or,
2) The hero does not achieve the goal and realizes the goal was a false lead and he's better off without it. Happiness ensues. Or,
3) The hero does not achieve the goal and discovers a better goal and achieves it. (Best when the better goal was under his nose all the time.) Happiness ensues. (+ kittens)

Justice must be done.
There must be judgment, punishment, and restitution. If redemption can be worked in, even better, but it must be consistent with the character.
Dead kittens must be avenged as the kitten killer is brought to justice, wounded kittens must be healed, enslaved kittens must be released.. You get the idea.

Give a sense of what the hero’s life will be like after the story ends. 
What will life be like back at home for the protagonist? (Hopefully with kittens.)

Make sure the relationship arcs are resolving in the place they should. (There may even be a tiny relationship arc that is a mini-version of the story arc.)
Make sure minor plot lines are resolving in slower moments.

And hopefully everything ends up happily ever after, with kittens and rainbows and satisfied readers who buy more copies of your book to thrust into their friends' hands.