Businessman Ben Dunne, who gave Mr Haughey an estimated £1.3 million, said his thoughts and prayers were with Mr Haughey's wife Maureen and their children.
"It's still a very sad time for me," Mr Dunne said. "Unfortunately for me some things affect me emotionally more than other things and some deaths have a profound effect on me and the death of Charlie Haughey affected me that way.
"I had a lot of contact with him over the years. Whether I like it or not, I feel that some of my behaviour in the past had an effect on Charlie's life, and a bad effect and that saddens me."
Mr Dunne added: "One of my weaknesses unfortunately is my brain and some things, whether I've been responsible in a small way or a big way, can upset me very emotionally. What I am certainly sure of is that I caused him some hurt. That hurts me.
He said the Charlie Haughey he remembered was a man full of life. "I admired him because I think he could read the future extraordinarily clear and well in lots of areas. Some historians will find negatives all the time, but on balance the vast majority will look and I think the late Charles Haughey will come out with more pluses than minuses."