Can a horse be "set in his ways"?

Hi there ! This summer I plan on undergoing a project with my aunt and her 14 y/o ex-rodeo-was-once-severely-beaten-and-ab… quarter horse. Her friesians just learned to ride in the past couple months, and we plan on being riding buddies this summer. Problem is, the QH is very ground aggressive. She's owned him for 7 years and has always been so. He's perfect to ride, turns on a dime and is faster than any horse I know, but you have to be rough as hell with him on the ground, or he will trample/kick/bite you. I've been bitten several times. She said she once worked him in the round pen, that didn't do anything but rile him up even more. He won't let anyone touch him and get away with it. It's strange to me, because he gets a lot of confidence from me when i'm riding him, but is opposite on the ground. To control him I have to put the chain part of the lead line on his nose when he's wearing his halter, otherwise he'll bite or cow kick me. Should I be convinced, as my aunt is, that he's set in his dangerous ways ?