And yet, large corporations, especially banks, are continuously caught with blatant abuse of the tax code (e.g. the "cum ex" scandal in Germany, where banks outright looted the government) or their customers.

The problem is that the fines are way too low. What does a large corporation care about a fine of even a billion dollars? Spread out over the time of the violation, that's petty cash, and as long as the execs don't have to go to jail, D&O insurance will pay any personal punishments.