When God made a fool of the Egyptians (Exod. 10:2)

Exodus 10:2 and in order that in the hearing of your son and your grandson you may tell how I made fools of the Egyptians and about my signs that I displayed among them, so that you may know that I am the LORD."

The verb עלל (translated “make fools of” by the NET) occurs 7x in the hitpael (Exod. 10:2; Num. 22:29; Jdg. 19:25; 1 Sam. 6:6; 31:4; 1 Chr. 10:4; Jer. 38:19). The LXX translates it with ἐμπαίζω “mock” (6x) and καταμωκάομαι “mock” (1x; Jer. 38:19). It is translated by the NASB “deal harshly”  (Exod. 10:2), “make a mockery of” (Num. 22:29), “abuse” (Jdg 19:25; 1 Chron. 10:4; Jer. 38:19), “deal severely with” (1 Sam. 6:6), “make sport of” (1 Sam. 31:4). The ESV translates it “deal harshly with” (Exod. 10:2), “make a fool of” (Num. 22:29), “abuse” (Jdg 19:25), “deal severely with” (1 Sam. 6:6), “mistreat” (1 Sam. 31:4; 1 Chron. 10:4), “deal cruelly with” (Jer. 38:19).

Associative Field
Yahweh does this to the Egyptians through the plagues (Exod. 10:2; 1 Sam. 6:6), Balaam believes his donkey has done this to him (Num. 22:9), the men of Gibeah “know” and do this to the Levite’s concubine (Jdg 19:25), Saul fears the Philistines will do it to him if they find him alive (1 Sam. 31:4; 1 Chron. 10:4); and Zechariah fears the deserted Judeans will do this to him if he surrenders himself to the Babylonians (Jer. 38:19).

All of the uses of this verb in the hitpael involve physical harm to the object. Balaam’s case is the least clear, since he suffered no physical harm the two of the times he says that his donkey did this to him. Only one of the instances involved harm—his foot was crush against the wall (Num. 22:25). Because Yahweh is the subject, the verb cannot necessarily imply sinful action. The LXX’s understanding appears to be that this verb denotes not only harmfully abusive action, but also  the consequence of the abuse, that is, that the abused person is belittled, exposed to ridicule, or shamed by the abuse.

The Lexica
HALOT offers “to deal with someone wantonly, play a dirty trick on someone” and “to abuse” in Jdg 19:25. BDB offers “busy, divert oneself with … esp. deal wantonly, ruthlessly.” In NIDOTTE 3:423, Eugene Carpenter offers a rather loose and expansive treatment: “When used with persons the word indicates a destructive, abusive, or deceitful action/attitude toward others, such as to wipe out, kill; make sport of, mock, dally with; abuse; take advantage of; inflict pain/grief upon; exercise oneself in mischievousness, wantonness. For example, the Egyptians/Pharaoh are made sport of/dallied with by the Lord (hitp. Exod 10:2; 1 Sam 6:6). A Levite’s concubine is abused sexually, and Saul and Zedekiah feared abuse from various groups (Judg 19:25; 1 Sam 31:4, hitp.; Jer 38:19, hitp.). The consummate fool was Balaam, whose donkey sported with him (hitp., Num 22:29).” The NET note seems to follow BDB as mediated through Walt Kaiser: The verb ‌הִתְעַלַּלְתִּי‎‏‎ (hit'allalti) is a bold anthropomorphism. The word means to occupy oneself at another's expense, to toy with someone, which may be paraphrased with "mock." The whole point is that God is shaming and disgracing Egypt, making them look foolish in their arrogance and stubbornness (W. C. Kaiser, Jr., "Exodus," EBC 2:366–67). Some prefer to translate it as "I have dealt ruthlessly" with Egypt (see U. Cassuto, Exodus, 123).

Conclusion
I'm inclined to follow the LXX's reading. In the case of Saul, he didn't fear bodily harm per se, since he commits suicide, but the shameful abuse he anticipates in the process of being killed by the Philistines. If this is the proper reading, then God's plaguing of the Egyptians is not simply bring them harm, but exposing them to ridicule in the eyes of the world. This reading is supported contextually by Exod. 9:16's "so that my name may be proclaimed in all the earth" and historically by 1 Sam. 6:6 where the Philistine's recall how God dealt harshly with Egypt to its shame.