"Stop BROWBEATING her! Can't you see she's sexy?!!"
I agree with
@Christopher except his last statement about Helen. Helen definitely had a "sexy" and "playful" attitude.

She and Kirk didn't realize the supreme danger of the device until too late. Adams abused the machine for power; yes. Narcissistic? No evidence. Egomaniac and sadist? Maybe.


Remember, he was also under a short time constraint since Kirk needed to check in with Spock every four hours. When exposed by Kirk, he took it as a challenge, and he was confident in his ability to fix the problem with Kirk and Helen.
ADAMS: Excellent, Captain. I compliment you. Do you know Doctor Van Gelder was down on his hands and knees sobbing at this point? It was so gratifying. (edit. Sadist?) I'm so fortunate to have had a couple of excellent specimens to, to work with. I've learned a great deal.(edit. Egomaniac?)
As for
Whom Gods Destroy, it looks like a safe version of the machine was put into service for the very reasons Adams and Helen discussed about tranquilizers:
ADAMS: A neural neutraliser. Experimental. Actually, we don't expect to get much use out of it at all (edit. a lie). That beam from above neutralises brain waves, relaxes the patient's mind. Does them no harm, of course (edit. another lie), and the effects are only temporary (edit. possibly the truth).
KIRK: One question, Doctor. If it doesn't do any good
ADAMS: Why do we go on using it, hmm, Captain? Hope. Yes, yes, there's always that slight chance that it might do some good in the more violent cases.
NOEL: Tranquilizers are fine, Captain, but to continually pump chemicals into a person's bloodstream
ADAMS: Exactly my point, Helen. Yes.