Situation: A guy is 5' 10" and 220 pounds, with 32% body fat.
Nice guy: When feeling down, says, "I'm just a tub of lard. No matter how much I diet, 220 seems to be my equilibrium weight." When in a good mood, makes fun of self with comments like, "Well, at least I've overcome my anorexia," or, "Hey, if we all get marooned on a desert island, I'll be the last to starve."
Average guy: "Jesus, I can't believe I'm up to 210. I'm on a new diet and exercise program, though. I'll be down to 185 in two months. You watch." (His buddies have heard this before.)
Sociopath: Makes fun of "exercise faggots." Shakes his head with false sympathy and clucks over people who are "unhealthy skinny," or "addicted to working out." Does a lot of macho posturing and intimidates others with the implicit threat of violence, as he knows some will mistakenly assume there's a fair amount of muscle underneath the fat. Eventually either goes on the cocaine diet or gets liposuction.
Situation: A guy gets turned down for a date by a woman. What does he tell his buddies?
Nice guy: "Spurned again. Well, at least I'm getting used to it." Thinks, I'm such a loser.
Average guy: "Oh well. I guess she wants some rich guy, or something like that." Thinks, if only I'd gotten her into bed once, she'd have changed her mind.
Sociopath: "I coulda gone out with her if I'd wanted to, but I got no interest in a skank like that." Thinks, she is such a loser. But he is in fact outraged that she would turn him down, and subsequently takes every opportunity to belittle her looks, intelligence, personality, and accomplishments.
Situation: A guy loses a lopsided tennis match.
Nice guy: Says, "Wow, you're a good tennis player." Thinks, wow, he's a good tennis player.
Average guy: Says, "Hey, you're a good tennis player." Thinks, I just had an off day.
Sociopath: Begrudgingly says, "You're a good tennis player." Thinks, let the turd have his little victory, tennis is the guy's whole fucking life.