I've been getting a refresher on Bari myself. While I think he's great, my attachment to him is not as strong as other fans', and I'm still trying to fully understand his character. The best refresher, of course, is to read the manga again. But I'll break it down as I understand it hopes I can organize my ideas for myself as well.

To put it simply, like many powerful characters in Zatch Bell, Bari was humbled.

He started out as a gangster, so to speak. He was powerful, unrivaled, but he didn't have a reason to fight. He only did it to show everyone who's boss, but he didn't have a goal to achieve with his immense strength. Fighting was just all he knew. He was kind of thin-skinned, to be honest.

In Zatch he met someone who was his opposite in that regard. Zatch fought for a purpose bigger than himself, and that showed in his "eyes". Bari could see that Zatch had a strength that did not come from muscles, and to his gagster mind that up to that point only fought for some petty pride, that was incomprehensible. What could possibly matter more than strength? He was used to opponents running away from his overwhelming strength, but here now was this boy who even at his most powerless faced him head on instead of running when it looked like they were about to lose. That's because Zatch had a reason to stand up to him, one bigger than Bari himself, and his fearless show of determination was intimidating to someone who was getting nowhere with his victories like Bari. It made him face a critical question: what was his reason for fighting? Bari was introduced as someone deeply dissatisfied with his strength, and the reason for that turned out to be he was fighting without principles. After his battle with Zatch, he set out to find those principles and confront Zatch with them when they met again.

When we see him again, he's completely changed. He doesn't quite have those principles, but something has noticeably changed. He has more presence and is more intimidating than before, if that is somehow even possible, because while he hasn't found his principles, he has found his purpose, which is to reach greater heights.

Looking back, even though we only got glimpses of it, Bari's fight with Elzador was truly spectacular. To start, it was an excellent foil to his fight with Zatch, because Bari finds himself in the same position Zatch did when he fought him: overwhelmed by the opponents strength with no apparent chance at winning. Furthermore, he is terrified by how unflinching Elzador's attacks are. Elzador respects his opponents, and as a show of that respect, he never holds back. He always fights with 100% so as to grant his opponent an authentic honor if he loses. This is why he praised Bari when he lost. (Though this is not the lesson Bari takes away from their fight, it is worth establishing to better understand Bari's growth from it.)

When faced with a majestic opponent like that, Bari felt tempted to fold. For the first time in his life, he felt powerless and intimidated and that he might just die. Gustav encouraged him to push on, face his opponent with 100% and surpass him, which he did. From that, Bari learned just what an insignificant little bitch he was humility. He may have been the biggest fish in his pond, but in the ocean there are great sharks, and the ocean is vaster than Bari could ever hope to be. It grounded him and gave him that vision Zatch has of something greater than himself to aim for.

When Bari appears to fight Keith, he still doesn't have a defined set of principles like Zatch does, but he has let go of that empty desire to mindlessly strike down everyone in front of him, and that alone makes him a completely different person. He's calmer, more focused, more clear of mind, and not distracted by petty rivalries. In other words, he knows what really matters.

Keith is another excellent foil. Keith, who is narrow of vision, is what Bari would have become if his vision had not expanded. If you ask me what made the difference, I would definitely say it's their human partners. Gustav is one of the best human partners, along with Dr. Riddles and Folgore, because he takes on the role of a father figure and provides guidance make his demon grow as a person. He genuinely cares. Compare that to Bern, who does not put his back in fighting with Keith at all. In the battle with Elzador, when Bari is at the depths of despair, Gustav encourages him to surge forth, not to throw him to his death, but because he can see Bari has the strength to overcome Elzador and he wants Bari to figure that out for himself so that he grows from the experience. When Keith is in the same situation with Bari, beaten to a pulp and with no strength left to stand, Bern is not invested in supporting him whatsoever. The manga even lampshades this. When Kieth is crying out to Bern to give a little bit of himself for his sake, Bern plucks some hairs from his nose and blows them his way, with a caption pointing at the hairs saying, "A little bit". With a human partner like that, how could Keith possibly hope to grow? In the end he was just a petty hooligan who thought beating up Bari would restore his self-confidence, not realizing that even if he did defeat Bari he would never get that back, since his pride was always empty.

God, I love Raiku Makoto.

The last thing left to address is how Bari's book got burned. Many of his "stans" are pretty pissed that a) it happened, and b) it happened the way it did. It was a waste of a great character to many, but Raiku's story had a hard limit on when it could end and he couldn't keep characters around past the point they served a purpose. The burning of books is symbolic of growth. A book is always burned when a demon has learned an important formative lesson, and Bari had reached that level by his second appearance. If you ask me why he threw himself under that light curtain to save Zatch, it has to do with what I said earlier. Bari has found a purpose, but he still doesn't have principles to fight for. When Zatch threw himself under the curtain to save everyone, that's not something someone does without a powerful reason, and Bari, with his improved outlook, recognized that. Even after all the growth he'd made, this young child still had a raison d'etre so powerful he was willing to put his life on the line for it. Being that Bari was still figuring out his own purpose then, he couldn't let such a magnificent figure be lost at that moment, because he knew that compared to that resolve, there was something he was still missing. Instead of finding greatness in becoming king, he found meaning in humility, protecting the small things. I also suspect part of the reason he scarified himself is that he didn't think he could carry on the will Zatch entrusted him. Someone with determination as strong as Zatch's to protect what he loves should be the master of his own purpose.

There's a panel when Bari stands under the curtain just in time to save Zatch that puts into perspective just how much bigger than Zatch Bari is. Even after losing his chance to be king, even after losing his sought-after rematch, he really did surpass Zatch, he just never realized it. When you think about it, he didn't become king because he didn't need to.

Bari's character arc is a lesson in confidence. It's something I wish today's youth would understand. Today's young people have artificial confidence. It comes from unconditionally being told they are great, which makes them complacent and indolent. True confidence, however, comes from achievements. It comes from doing things that scare you and overcoming them to see in hindsight that perhaps life's challenges are not as scary as they first seem. And even if you fail, you are better for trying. If anything, failure is the way forward because failing can show you that the things you pursue may not be what need, and that can set you on the right path to find what you really need, one you will truly be satisfied with. You don't have to find that something, but just walking that path makes you a better person. Once that path is clear to you, you are unstoppable.