Albert Barnes Commentary Exodus 18:11

"Now I know that Jehovah is greater than all gods; yea, in the thing wherein they dealt proudly against them." — Exodus 18:11 (ASV)

Greater than all gods - See Exodus 15:11. The words simply indicate a conviction of the incomparable might and majesty of Yahweh.

For in ... above them - that is, the greatness of Yahweh was shown in those transactions in which the Egyptians had thought to deal haughtily and cruelly against the Israelites. Jethro refers especially to the destruction of the Egyptian host in the Red Sea.