The three big mistakes Tony made that comes to mind are.

1. Promoting Chris to Capo, before Chris was cleaning up.
2. Favoring Tony B
3. Making Johny Sac and Phil angry with him and pretty much rubbing New Yorks nose in it with his greed.

"I have this Nightmare. I'm on 5th avenue watching the St. Patrick's Day parade and I have a coronary and nine thousand cops march happily over my body." Chief Sidney Green