How to describe a powerful SUNDER!

[Cranky Dog]

In my game tomorrow, there will be some nasty sundering from an oni fire yai wielding a tetsubo (maul) of the Titans (triple damage against inanimate objects).

Combined with the oni's power attack and vital strike, it can sunder and destroy the equivalent of a +5 full plate (20 hardness, 95 hps) or a 2in thick wall of adamantine with a single hit and leave the wearer completely unharmed.

How do I go describing a monstrous giant smashing your armor with a huge overhead chop, while leaving the wearer right as rain, not even slightly dazed, staggered or stunned?

[Unlighted]

Hanzo watched as the giant figure raise its mighty weapon high into the air. He knew that he wasn't agile enough to evade the attack completely so he braced himself against the incoming impact. The maul came down with a grunt of effort from its wielder. Hanzo put his thick shoulder plate into its path trusting in his sturdy armor to protect him from the worst of it. A thunderous clang rang out as weapon and armor collided in a contest as old as war itself. Hanzo grunted as his knees flexed absorbing the momentum from the maul. The fact that he wasn't a bloody mess on the ground meant his armor had saved him yet again. He opened his mouth to mock his opponent when with a loud CRACK! multiple fissures radiated out from the maul's impact point. Hanzo could only watch horrified as the fissures created a tapestry of destruction across his full plate. The armor that had protected him for so long fell apart in a clatter of metal rain at his feet. The only other sound was the laughter of his opponent as he raised his weapon for another blow.

It kind of become its own mini story, but you get the general idea. :)
Your best bet is to get across the power of the attack, but not completely dismiss any impact on the character. If I got hit with such a weapon I would expect to at least be rocked back on my heels or somesuch. Suspension of disbelief only goes so far, even in a fantasy setting.

If you were dead set on destroying the armor, but having absolutely no effect on the wearer you could just use the good old magic out.

The weapon smashed into Hanzo's armor with a bright blue explosion engulfing him in its radiance. As the light dimmed Hanzo stood unharmed, but his armor lay in pieces upon the ground.

[Third Mind]

I'd guess it depends on your Oni's personality.

Perhaps the Oni, being as ancient as it could be, has become so proficient with it's weapon that it is amazingly accurate in controlling it. Stopping the blow short from destroying his opponent on purpose in order to toy with them and take away that which they felt would keep them safe.

Something like Unlighted said:
"The oni lifted its massive maul above its head with ease and a grin before swinging it downward upon its intended victim. Just as the blow struck the heroes armor the maul stopped mid swing, it's followthrough halted. The hero looked up to see the oni's grin widen. But why? The hero hadn't felt a thing. It was then the hero's eyes widened in realization as the looked to the ground. There, upon the soil, lay the shattered remains of what once had kept them safe. Their armor, left behind by past generations, was now in tatters, lost forever. The hero looked up as the oni once again lifted it's maul and the hero didn't know yet if the oni intended to finish him, or their weapon."

[Karl Hammarhand]

I like the idea the oni is a master of his weapon and can target what he likes.

[Dustyboy]

Dahh, he's a weapon master, I feel as though he can stop it on a dime, targeting the armor, shattering it with force, and then continuing on.

[Dustyboy]

Sorry to DP but I'd also imagine that the magical force of the armor would have a recoil as it disperses, which could be what pushes the hammer back from killing the wearer

[Lurk3r]

I once had a 3.5/PF goliath fighter specialized for sundering. We started at level 8, so I already had Greater Sunder. The first encounter of the campaign was a bunch of low level bandits with short swords. Naturally, I start off by trying to sunder one of their weapons. I rolled high and did enough damage to kill him with the damage that carried over after breaking the sword.

The GM narrated that I went right through the sword and sundered his head.

[blahpers]

"ONI BROAK UR THING LOLZ"

[Fomsie]

JUDO CHOP!

or just, Oh SNAP!