Say you have a protagonist who, at the start of a story, has been through the absolute ringer (death of a loved one, betrayal, hunted), they're at their lowest point. How then do they rise up out of their funk? Like I'm kinda leaning towards another character helping them, but is that enough?
Sounds like you are talking about resilience - the ability to come back from hardship stronger than you were before. Resilience depends on your own inner resources. Here's a link to The 7 Main Characteristics of a Resilient Person Another thing that helps people bounce back is meaningful human connection and helping others. So, instead of having someone else help them, I would have the person who is at the low point help someone else. That gets them out of themselves, and their funk, as they put their focus on someone else.
Having the hero help another character? I like that! Something that gives the character a glimmer of hope!
I like to use 'the smallest act of kindness can mean the world to someone else's type of element. Like a story I read where this guy helps another because they dropped their books. Because the man was nice, he helped him pick them up. For the man it was his nature, help and move on, no further interaction. But for the person being helped, they need up not killing themselves that day.
Going through hardship often does bring growth. But that requires contextualizing it so it carries meaning, rather than feeling sorry for yourself. Hardship without a positive context is mere victimhood, and that halts growth. What causes growth is shouldering your burden without complaining or blaming others. It's mostly these hardships that break us out of our little self-referential (immature) frame of mind and make us see the bigger world we're a part of. In fact it might be true that after reaching adulthood all growth comes from either bearing hardship without malice, or from being able to find meaning (context) in things.
I'd say you learn to see more value in yourself and in others and in the world. Basically I'm saying "Do unto others as you would have others do unto you." Psychologically it's known as 'retracting your projections onto other people'.We have a tendency to project our own worst traits onto others. It makes us feel like we've gotten rid of the bad traits in ourselves. Otherwise known as scapegoating. If a person or a group projects all their worst traits onto one person (or a goat maybe) and symbolically kills them by sacrificing that person (or goat), then for a while they feel like they've purged themselves of evil or of all their bad tendencies. It's a nasty habit we have. Think about the Salem witch trials for instance. But of course it doesn't work, since the bad traits or tendencies were never really in the sacrificial victim, they were in us and that's where they still are. Instead we need to admit they're in us, and do some psychological work to make ourselves better, which always begins by admitting honestly what our faults are. Especially the ones we've been projecting onto other people or onto situations. Basically it's growing up, since blaming your problems on other people or on a situation is a childish thing to do. Of course to some extent other people do contribute to our problems, and it's no good to blame yourself for problems others really did cause. It's no good to blame or hate at all in fact, that's the biggest part of the problem. You need to be very honest and see where the line really is. But still it does no good to feel hostility toward other people, unless I suppose they've done something really unforgivable. Even then the best course is probably to get them out of your life and try to find a way to understand if not forgive. Understand that we're all weak and wounded and tend to hurt others in self defense. It's better to understand that they too suffer from the human tendency to blame others and to pile your problems on others and sacrifice them to try to purge yourself of sins. Another take on it is what was said by Aleksandr Solzhenitsyn after spending several years living in Soviet gulags (prison camps) where he suffered horribly and saw many people around him tortured and killed: “If only it were all so simple! If only there were evil people somewhere insidiously committing evil deeds, and it were necessary only to separate them from the rest of us and destroy them. But the line dividing good and evil cuts through the heart of every human being. And who is willing to destroy a piece of his own heart?” ― Aleksandr Solzhenitsyn, The Gulag Archipelago 1918–1956
I'll try to move away from the vague generalities and be a little more specific. Though that's hard since the question itself was posed in vague generalities. If you've lost a loved one and been betrayed, of course grief has to run its course. There's no rushing that process, it just takes time and a lot of it. But maybe after a certain amount of time, I mean before full recovery or healing can happen, the character could at least reach a point where the suffering is less intense and can be endured better. There are many stories and movies built around revenge, and most of them concentrate on the well-known fact that living to get revenge destroys you and leaves you a hollowed-out empty husk. What's far better than revenge (which is projection writ large) is to find renewed meaning in your life, something positive to move toward. A goal. Think of it as a symbolic death and rebirth. He has died as who he was, the imperfect person he used to be, and his life as it was is now over. He's gone through the wringer as you said. But now is the time for the rebirth to begin. Redemption is built on the ashes of the old life, and grows gradually to blossom and burst forth into a renewed life as a different person now, one who has learned and grown internally from what he's experienced. To accomplish this you'd want to have the character start with a fatal flaw (fatal meaning not that it kills him, but that it's related to his fate, it brings it to fruition—well and symbolically I suppose it is what kills him). The flaw destroys him, causes his misfortune. But along the way he learns important lessons that change him, he overcomes the flaw that destroyed him and emerges as a new and better person. In fact this is the typical hero's journey type of story structure. The journey through the underworld is the symbolic death, and the return to the land of the living, now bearing the sacred elixir or the magical amulet or whatever prize he won through his struggles, is the regrowth or redemption or resurrection.
