Exodus 18:11

Now have I known that the Lord is stronger than all gods; for by the very thing by which the Mizraee wickedly would have punished Israel by (drowning them in) the sea, upon themselves came the punishment, in being punished in the sea.

FOR IT IS IN THE THING THAT ‘ZADU’ UPON THEM. The meaning of this is that in the matter wherein the Egyptians premeditated on the basis of zadon (premeditated, conscious sin), as is explained further in the text. [their wickedness] against Israel, I [Jethro] now know that the Eternal is greater than all gods. And the purport thereof is as follows: Due to the fact that G-d had decreed upon Israel, and they shall enslave them, and they should afflict them, there would have been no great punishment meted out to the Egyptians. But they acted presumptuously against them, and intended to eradicate them from the world, just as they said, Come, let us deal wisely with them, lest they multiply. Pharaoh commanded the midwives to kill the male children,, Verse 16. and he decreed upon [all his people, saying], Every son that is born [unto the Israelites] ye shall cast into the river., Verse 22. It was due to this that there came upon the Egyptians the kind of punishment which utterly destroyed them. It is this principle which is expressed in His words, And also that nation that made slaves of them will I judge, as I have explained. (Vol. I, pp. 203-205.) Now G-d saw their intentions, and He took vengeance upon them for the wickedness of their hearts. And thus does Scripture say again, And Thou didst show signs and wonders upon Pharaoh… for Thou knowest that they dealt insolently against them, for the punishment was because of the wicked plans they devised to carry out against the Israelites. Thus the Eternal looketh on the heart, and executeth justice for the oppressed, avengeth and is full of wrath, and no one can deter Him.
Now Onkelos translated [the above Scriptural expression] thus: “for by that very thing with which the Egyptians thought to judge Israel, they themselves were judged.” By this rendition, Onkelos meant to say that their punishment came because of the drowning of the [Hebrew] children in the river, which was not part of the Divine decree, and they shall enslave them, and they shall afflict them. Therefore, He destroyed them by water.

מכל האלוהים. None of these other deities has the power to avenge their worshipers from unjust sufferings they have endured.

כי בדבר, meaning that G’d requited for every sin committed by the Egyptians in an appropriate and fitting manner. This is the basic meaning of the insight Yitro had now gained.

כי בדבר אשר זדו עליהם. G’d saved the people by using the very means the Egyptians had used to harm them to harm their oppressors. The word זדו, past tense, occurs as future tense, יזיד in Exodus 21,14 describing the deliberate commission of a crime, a sin. The sin Yitro had in mind was that G’d had killed the Egyptian firstborn as a retribution for the male babies of the Jewish people having been thrown into the river to drown. (Exodus 1,22). The Egyptians died by drowning just as their victims the Jewish babies had died by drowning. Yitro recognised that the ability to make the punishment fit the crime is what put our G’d in a class all by Himself, unparalleled in any other religion. None of G’d’s agents in the celestial spheres, even, would be able to do this.