In high school, I had a close-knit group of friends, many of whom remain good friends today. Except for one, a person with whom I was remarkably tight for an intense period, and then it all fell away. (Let’s call him X, because X is a fine name for something buried, though “treasure” doesn’t come to mind.) X probably had the most ranging intelligence of all my friends, the quickest wit and certainly the most ingenuity: he was the kind of a guy who would look at a dead radio, and in five minutes solder a spoon into its wiring and make its silence sing again.
But for all his charisma—and he had that—my friend had a sharp edge to him that impelled him to practical jokes, many of which seemed less than funny. He would put raw eggs in our beds that later made for soggy sleeping, soap our toothbrushes, surreptitiously tie some of our shoes together when in a group so when we got up we would stumble. He drove his Volkswagen van around a big tree in my tight backyard at mad speeds with my parents home and watching, so that it seemed like a demon’s visitation—what was that? He once dumped a full bowl of cereal and milk on me while I was sleeping, for no reason other than the feeling moved him. Because he worked in a pizza parlor, now and then he’d drive by, get out and throw entire pizzas on our roofs.
The moment that turned the corner for me was when he tied a string to our front door so that the bag of charcoal briquets that he’d tossed on the roof above would fall on one of us when the door was opened. The fact that it came down on my mother was the catalyst for what followed. All of my friends, my brother included, had some kind of grudge against him. “Remember when X spit in your drink and waited for you to swallow some before he told you?” “Yeah!”
We all had the stories. So we decided to humiliate him.
A couple of our group (also X’s victims) dropped out, leaving me, my brother, and two other friends, all of whom had suffered at X’s hands. Because all of them also worked part-time in that neighborhood pizza parlor (excepting me—I understood from an early age that work was unhealthy), they knew the routine: whoever was the assistant pizza “chef” would need, maybe an hour into the shift, to go to the refrigerated, locked storage shed out in the alley that flanked the shop, in order to bring in one of the five-gallon buckets of shredded cheese. We knew X’s work schedule, and we knew he would come out. We were waiting.
We were hidden in various places in the alley: behind dumpsters and the projecting side of a building. We had a dozen raw eggs and 10 water balloons. I was on top of the shed, hunching in silence, with two plastic buckets of tomato sauce. When he came out, we unleashed a fusillade of high-school-boys-mad-as-hornets hell on him, while howling imprecations.
Our work was effective. He was a miserable sight, soaked, stained, cowering. He didn’t say a word, but just stood blinking and defeated.
With that, everything changed.
He had been one of the mainstays of our group, in the way that kids can run in packs—friends for all time. But after the attack, he simply backed out. No calls came or went in either direction for a long time. After a while, we started to see him socially again, on the fringes of our group’s activities, but the tenor of our relationship had strongly shifted.
I felt the most sympathy for him, because I was closest to him, and admired many of his deep skills, but our relationship changed forever. I still hear from him every few years for some incidental reason, but from atop that storage shed, the deep comradeship fell to its death. We’ve never had a conversation about what happened.
But what happened after what happened is why I bring the incident up in a writing forum: I’d always thought that X would be the biggest achiever of our group, a senator, owner of a global yachting franchise, a motivational speaker a la Tony Robbins, a scientist entrepreneur a la Elon Musk. But he became (and is today) a real estate salesperson.
The Aftermath (for Friends, for Your Characters)
I make no judgement whatsoever on his chosen profession. What I’m prying into is whether the humiliation, whether the shaming from his allies, whether the absolute rejection implicit in the event—and its lasting consequences of losing his closest friends—affected the course of his life in any deep way. And here we—finally—get to what this has to do with writing. I don’t know what happened in my friend’s case, but I do know that you can certainly use a life event of reverberant consequence—and in this case, utter humiliation—as the fulcrum for a long arc of story that informs telling aspects of your characters.
I don’t know what happened in my friend’s case, but I do know that you can certainly use a life event of reverberant consequence—and in this case, utter humiliation—as the fulcrum for a long arc of story that informs telling aspects of your characters.
The main character in my first novel is humiliated when his high school best friend sleeps with the girl he is dying to be with. He makes some bad, perverse decisions after that that violently shake his sense of himself. But those betrayal/mistake events happen fairly close in time. The kind of humiliation (and in my next example, ugly abuse) I’m getting at, which carries looming, evolving emotional power is something you see in the movie Mystic River,  where the Tim Robbins character, abducted and abused as a youth, carries deep scars that devastatingly surface many years later.
In the collaborative novel I’m working on now, the lead character shows all the signs of having been humiliated, shamed or attacked in his past: low self-esteem, lack of trust, unreliability, withdrawal, and impulsive behavior that he puzzles over later. However, my co-author and I haven’t given enough hints or openings into his backstory that will provide the “so that’s it!” understanding for the reader. Of course, you wouldn’t want that backstory spelled out in some neatly packaged explanation: one person’s humiliation could be more motivation than morbidity. You’d never want the variant ramifications of dark events to be rendered as a psychology class.
Backstory: Less Effective Dumped as Tomato Sauce
You’d also never want your readers to see the backstory of some engulfing event from the past unswervingly directing the course of the character’s life, like a Calvinistic kind of predestination (more of a “you pay for what you get” rather than the opposite). And the revelation of such an event needn’t be given a flashy flashback scene, so that its crux is magnified and its consequences thus made to seem inevitable. For me, those backstory elements, even big ones, are best woven in, so there is buildup and reader recognition through a glass (page), darkly. Unless the event IS the launching and core of story, such as in a novel like The Lovely Bones. 
There have been some great posts on backstory on WU; here are a couple from Lisa Cron that examine its use and implications much better than I can:
Psychic injuries, especially when we are young, seem to keep their talons sunk in our flesh, even if the attacking harpy is long gone. Something to do with that sick way our brains hew to the negative memories of a time when the cowl of darkness has descended—we seem to so freely forget the bright moments. But of course, your characters shouldn’t just overcome, by rote, that shattering event. Some stories are built on characters having to continually stare down the darkness—or abide in it.
There probably would have been a better way to deal with X. But I was stupider back then, and didn’t draw on rational resources. But now, there’s a chessboard of characters—beware, pawns!—available in which to play out my all my past pathologies. Maybe one will even apologize.
So, ever dumped buckets of tomato sauce on one of your best friends? Can the fact that we humans are also red in tooth and claw make for a significant current in your tales? Speak, or forever have eggs in your bed.