How was Emes missing?
Radak: It was not found among them at all, as if it never existed.
Malbim: Initially it was among them, just it stumbled while going among them. Afterwards it was totally missing from them - they did not know at all what is Emes.
Why is "Sar me'Ra Mishtolel"?
Rashi: People establish him to be a lunatic. This is like "Eilecha Sholal" (Michah 1:8). The Targum of Shogeg is Shalu. Also "Al ha'Shal" (Shmuel II, 6:7, refers to Shogeg).
Radak: It is not found, as if they Shalelu and Bazezu (plundered) it from the world.
Malbim: If one was found who refrained from evil and Aveiros Bein Adam la'Makom, it was not intended. He forgot to do evil. If not, he would have done evil!
What will be the consequence of being bad in Hashem's eyes?
Rashi: Therefore, He brought punishments on them.
Why does it say that Hashem was upset only about the lack of Mishpat?
Radak: This is harsher than the others, for without Mishpat, society cannot stand. Chazal said that theft has great power [to bring punishment], for Dor ha'Mabul transgressed everything, and their decree was sealed only due to theft - "Ki Mal'ah ha'Aretz Chamas Mipeneihem" (Bereishis 6:13).
Malbim: Via this, people cease to be human; they are like wild beasts. Via lack of Tzedakah, they cease only to be people with a creed.