Never pick a fight with an old man, if he's too old, his "Momma" died, and he doesn't give a (insert expletive), he'll just kill you. Or if your lucky, kick your a**, and leave you knocked out for 20 minutes,....
This dude is just not the one to pick on. Granted he kinda doesn't back away from any confrontation, he looks in great shape for 60+ years old.
I believe the word is:
or·ner·y
1.
ugly and unpleasant in disposition or temper: No one can get along with my ornery cousin.
2.
stubborn: I can't do a thing with that ornery mule.