Throughout the Torah, the various Egyptian Pharaohs are always referred to as simply "Pharaoh" or "the king of Egypt" (or both), but never with any other parts of their official titulary.
By contrast, in Nach, some of them are also left otherwise unidentified (such as the one whose daughter Shlomo married), but for others a name is given:
- Shishak (I Kings 11:40 and 14:25, II Chron. 12:2-9)
- So (II Kings 17:4)
- Necho (II Kings 23:29,33-35; Jer. 46:2; II Chron. 35:20-22, 36:4)
- Chofra (Jer. 44:30)
And to top it off, some of the ones who are named in some places are unnamed in others. For example, Yechezkel, even though fully four chapters of his book are devoted to prophecies of the downfall of Egypt and its king, never names him as anything other than "Pharaoh" or "king of Egypt" (though we know from the events as described by Yirmiyahu that they refer to Chofra).
Does anyone address the reason for these differences? [If it's because the Torah didn't want to use any of their names, all of which refer to various Egyptian deities, then the same should be true in Nach. But, after all, the Torah seemingly has no problem mentioning other idolatrous personal names of non-Jewish figures, such as the Edomite kings Hadad (Gen. 36:35) and Baal-Chanan (ibid. v. 38).]
(In a comment, DoubleAA pointed out that the same thing can be asked regarding the Avimelechs of Philistia: they are referred to only by that title in Chumash, and mostly also in Nach; but the one of David's times is usually identified by his personal name, Achish (except in Ps. 34:1).)