I have a problem with my in-law . . .
 

. . . and he's Tar-Palantír.

It seems that, for all the good he had done in his life, he made one mistake. One possibly fatal mistake.

If Tar-Palantír would indeed repent of the deeds of his forefathers, would he not follow this custom, passing the sceptre to his heir (Míriel) before his death? Would this not have saved Númenor from the machinations of Pharazôn? I know that a majority of the Númenóreans were already corrupted, and that little could change that, but still, would this have resulted in a different - perhaps milder - outcome?

You do have a point there about Tar-Palantír.

It might have done some good, but then again it might not. Pharazôn seems a rather determined character.

I think he did pass the sceptre to Miriel- but it still didn't stop Pharazon. From Akallabeth-

If there's a will, there's a way...
 

And there is indeed for Ar-Pharazon. He would have openly opposed Tar-Palantir while he yet lived or not, but as soon as he dies, the gears will kick in motion. Undoubtedly he would still have done the same thing.

I think he didn't.

If Pharazôn is as headstrong as you think he is, wouldn't he have challenged the rule of Tar-Palantír outright? He commands a majority in Númenor, and could have used that for his imperial ambitions. But he didn't. He respected - or at least feared to oust - the holder of the Sceptre. Seeing Tar-Palantír dead without properly passing the sceptre gave him his chance - it is easier to challenge a law - especially a radical one made for personal reasons - than a living person, I think.

So he might be determined. But I don't think he would challenge a Tar-Míriel, Ruling Queen of Númenor.

Ar-Pharazon's such a chauvinist that he thinks even ruling queens are beneath him, I presume?

Or he took advantage of the temporary setback caused by the sudden change of the ruling monarch.