Although I would myself consider injuring an opponent in certain situations (e.g. where I am unlikely to survive a second attack), I don't know of any aikido 'techniques' which are designed to injure someone. Which techniques are being reffered to?
For example, although kote-gaeshi can break a wrist, kaiten-nage, shiho-nage and sumi-otoshi can dislocate the shoulder, sankyo can cause a spiral fracture, irimi-nage can break someone's neck/knock them unconcious, ikkyo can be used to break an arm etc the changes Ueshiba made to these techniques are such that this doesn't occur.
If kote-gaeshi is breaking wrists, it is possible that the uke's body is not been thrown properly and they are just being expected to 'leap' over. Also, I've recently found that nikkyo can be applied without pain by moving the locked wrist down, and stepping slowly backwards. If they try and resist the motion it is painful, but the actual down motion is not (obviously hard to explain in words).
Also, I've mentioned on another post that, though yonkyo is painful, the pressure point can be used in shiatsu to relax someone and calm them down.