Re: The use and strength of atemi application
Atemi in aikido are not primarily to do damage - they are used mostly to distract or unsettle the attacker as Mike and Ahmad said. And in aikido mostly we try to be relaxed but full of energy - that is different from some other martial arts that deliberately transition from a relaxed state to a powerful focus. But relaxed doesn't mean soft for atemi.
Simon also mentioned the pressure points and for example you can do atemi against a specific point with the knuckle of your middle finger or forefinger protruding.
And any time you can get help from the angels you should take it.