I did not delete anything. I'm not familiar enough with BitCoin-QT files (yet) to know what is appropriate to delete.
If the reindex fails, you should delete the highest numbered blk*.dat and rev*.dat files in the blocks/ folder in the datadir.
I think maybe for small users like me, with no understanding of application internals, BitCoin-QT application may not be sustainable.
This rarely happens and is usually not Bitcoin Core's fault. In many cases, it is just spurious/random corruption (cosmic rays, random bit flipping, etc.). Other times it is a hardware problem.