Your correspondent asks about contracts that were broken. The best and most glaring example of a broken contract (covenant) that I am aware of is that between God and the Israelites regarding the Promised Land.
Beginning with GE 12:7, 13:11-18, GE 15:7, GE 15:18, GE 17:1-27, God makes his covenant (first with Abram (Abraham)) regarding the Promised Land, the "land of Canaan, for an everlasting possession." The covenant (unfulfilled) is renewed with Isaac (GE 26:3). Then (still unfulfilled) with Jacob (GE 28:13-15 and GE 35:1-13). Jacob repeats this (unfulfilled) promise to Joseph (GE 48:4). Joseph repeats the (unfulfilled) promise to his brothers. God repeats this (unfulfilled) promise to Moses (EX 6:4, 8).
Beginning with Moses (around NU 14:20), God starts telling Moses all the reasons that the promise has not or will not be kept without modification (NU 14:20-30, NU 20:12, NU 20:24, NU 23:31-33, NU 27:12-23, NU 32:10-13, NU 33:50-56, NU 34:1-15, DT 11:22). As the possibility of occupying the Promised Land seemed to get nearer, the conditions for its fulfilment and the reasons that it did not occur multiply.
Moses repeats the promise to his people in DT 4:31, DT 7:9, 7:12, and more conditions are added in DT 8:1, DT 10:12-13, DT 11:8, DT 11:22-24, DT 28:15, 36, 58, 63.
The (unfulfilled) promise is repeated to Joshua (JS 1:3-6).
In JS 11:23 and 21:45 it is claimed that the Promise was fulfilled. In reality, however, the Promise was NEVER fulfilled. GE 12:7, GE 13:11-18, GE 25:18-19, GE 27:8-14, NU 33:50-56, NU 34:1-15, and DT 1:7-8 show that the boundaries of the Promised Land were elastic, and at times were wide enough to include everything between the Mediterranean and the Euphrates. In any case, there was no everlasting possession.
Thus, the Promise which the OT alleges was made by God to Abram -- the first OT prophecy -- is the first unfulfilled prophecy. This can be seen in the necessity to revise and repeat the prophecy through succeeding generations from Abram, to Isaac, to Jacob, to Joseph, to Moses, and to Joshua, and to add condition after condition as the fulfilment encountered repeated delays. Although Joshua eventually succeeded (according to the Bible) in conquering the land of Canaan, it has certainly NOT been an everlasting possession (as originally promised) nor does Canaan encompass the entire territory that was sometimes promised.
"It is not to God's credit that the Jews have been more faithful in keeping their part of the bargain than God seems to have been in keeping his part of it." (p. 101, "Jesus in Bad Company" by Raymond E. Brown, SS)
Regards, Don