What level of wealth and power?

No, Billy was never a nice person.
Going all the way back you have stories of Billy screwing over people and developers.

Billy also had a lot of "funding" to "build" his company.
Other entrepreneurs who made smaller mistakes had to close up shop.

So... if you actually got corrupted by wealth and power, as the myth suggests...
actually, it is more like alcohol. If you are violent angry person inside, then alcohol will magnify that.

If you actually look at real entrepreneurs.
People who actually create a multi billion dollar companies, they are all down to earth people. People you would really like as friends. People who really care about their employees and their businesses.

What i see when they say "wealth and power" corrupts is just a smoke screen.
Because the ruling elite, the 13 families are all psychopaths.
And for their faceman, they find other narcissists and turn them into full blown psychopaths and promote them into positions of power (like congressman and presidents)

Lastly, Billy has no real money. If we actually had a top 100 wealthiest families, Billy might not even make the list.