He'd already be off-balance because she's burned his face and he's probably already clawing at it. If he was stood with one foot on her and the other on the ground alongside it's not the most stable position. He'd probably have most of his weight pressing on her, the triumphal pose of someone sure of his upper hand, ready to deliver the finishing blow.
He'll also be dealing with the shock of the sudden reversal of fortune. Think of the emotions, not just the physical actions. You've done judo in your time so you'll know that a fight is only partly physical. Until the flame hit him he knew he was winning. His eyes have probably instinctively closed to protect them from the flame.
Now add in the fact that whether she slashed or thrust her body would have moved to accommodate the sudden action, either sideways or upwards, which would interfere with his already precarious balance. Judo thinking again, exploiting a poor balance.
If she cut through both his legs he's probably going to tip to whichever side she cut first no matter how close the cuts, just as a tree falls to the notched side.
If she skewered him upwards he's going to rear backwards and fall that way.
Once the weight is off she can roll in the appropriate direction and regain her feet.
The only downside to the upwards thrust through the length of his body is that the muscle spasms would clamp so tight around the blade it might well be snatched from her hand as he falls, so she'd need to find another weapon.
But the sudden flame would have mentally unbalanced everyone else for a few useful seconds. They'd be instinctively backing off.
You know the old saying about 'don't bring a knife to a gunfight'? Your sword or hand held thrusting-spear would suddenly feel pretty inadequate against an unexpected flame-thrower, wouldn't it?
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You can't shove all that explanation into a fight scene without slowing it down, but you can show most of it by concentrating on the victim's reactions more than the cause. This is how a good theatrical fight works without any real danger. The audience sees a man fall back and assumes he's been struck.
Here we are creating the same effect with words.
Gyppo
