If a tecnique is applied, and the basics are perfect, it is almost impossible to resist. Master Thamby Rajah 9th dan, I trained with him. The guy is tiny but the biggest guys just could not resist his nikajo (nikkyo). Most middle range students like us, if someoine resists we can often apply a diffrent tecnique to counter his counter. Read total aikido we Soke Shioda, read the second to last chapter, his explains how his advance students ,learn to apply tecnique against resistance.
We had one guy come in once to our exeter class. He was a car mecanic about 6' 6'', probably about 25 stone heavy (sorry about imperiual measurements, its heavy) and the rumour was the his unscrewed car wheel nuts with his bare hands. With his hand relaxed, he would'nt go limp at the wrist like any normal hand. I wenty to apply nikajo on him, but to no avail, thus I put on sankajo and he was yelping like a baby. The head of our club got it on him with sheer movement. He brought him to his knees, just by cutting the nikajo through his weak line, his said he felt no pain in his wrist, he just felt his balance go and he slumped down. The master Thamnby Rajah guy I mentioned earlier, applied yonkajo in such a way that, I felt nothing on my wrist, but suddenly my knees gave way????,,,?? yeah wierd, someting to do with nerves in the anatomy. what we've gotta realise is that the tecnique (i.e. pain in the wrist etc etc, doesnt matter that much, its mainly the balance). Get the timing, distance and balance correct and the tecnique will be devastating.
But its not that easy.