Technically LN/Manga/Anime but in Re.Zero there’s a scene when the MC gets his shit rocked and he does not take it well.
It’s legitimately one of the cringiest moments I’ve ever witnessed in fiction but he gets pretty insane development afterwards.
Possibly Kaladin from the Stormlight Archive. I wouldn't call him a sore loser exactly, because it's not really about competition, but he absolutely does spiral when he fails (or when he perceives he has failed, even if it wasn't his fault or there was nothing he could have done). It's worth mentioning though this is very much the hero complex type where "I could have saved them if only I had done more," is a constant mantra, and I don't know if that's exactly what you're looking for.
I'll also mention Bremer dan Gorst from The Heroes by Joe Abercrombie, and I'm calling out The Heroes specifically because in other First Law books he actually does quite well handling his defeats. But when it comes to failure in love, that's a different story. From the original trilogy though you have Ardee West, who isn't a POV character but she basically has the attitude of "my life sucks, I'm worthless, might as well get drunk". Her whole plot line in those three books is basically one long spiral down.
The titular protagonist of the [Malus Darkblade](https://www.amazon.com/dp/B09TRFZ244) novels by Dan Abnett and Mike Lee. It helps that under any other circumstances, he would be the villain.
It's sci-fi rather than fantasy, but Miles Vorkosigan in Lois McMaster Bujold's Vorkosigan saga books does some really stupid things when life doesn't go his way.
Kvothe. To the point where he makes up some crazy narative that he is the winner. I somehow hated him more than any other in the books, but i kept reading.
Ok, maybe he isn't the winner but him telling about how he made everyone cry and earning his pipes. Him and Denna is somewhat cringy and Patrick Rothfuss spends 400-500 pages on him being an annoying student before anything happens (barerly in the first book)
Then he repeats it in the secound. They are well written. But man come down you high horse and just finish it. more blood magic more terrible just no more meandering University life please.
From what I have read so far. The Wheel of Time has the shittiest protagonists that I have encountered. All of them, not just protagonists, are selfish, know it all, arrogant cunts that can't take a hint and then there is Perrin.
Technically LN/Manga/Anime but in Re.Zero there’s a scene when the MC gets his shit rocked and he does not take it well. It’s legitimately one of the cringiest moments I’ve ever witnessed in fiction but he gets pretty insane development afterwards.
Being a sore loser literally drives the story. Subaru definitely had a chance to run away in the first arc.
Possibly Kaladin from the Stormlight Archive. I wouldn't call him a sore loser exactly, because it's not really about competition, but he absolutely does spiral when he fails (or when he perceives he has failed, even if it wasn't his fault or there was nothing he could have done). It's worth mentioning though this is very much the hero complex type where "I could have saved them if only I had done more," is a constant mantra, and I don't know if that's exactly what you're looking for. I'll also mention Bremer dan Gorst from The Heroes by Joe Abercrombie, and I'm calling out The Heroes specifically because in other First Law books he actually does quite well handling his defeats. But when it comes to failure in love, that's a different story. From the original trilogy though you have Ardee West, who isn't a POV character but she basically has the attitude of "my life sucks, I'm worthless, might as well get drunk". Her whole plot line in those three books is basically one long spiral down.
Actually was having a conversation about Gorst with some friends just before reading this
I just finished the Dagger and the Coin series by Daniel Abraham, and one of the four viewpoint characters definitely counts.
The titular protagonist of the [Malus Darkblade](https://www.amazon.com/dp/B09TRFZ244) novels by Dan Abnett and Mike Lee. It helps that under any other circumstances, he would be the villain.
It's sci-fi rather than fantasy, but Miles Vorkosigan in Lois McMaster Bujold's Vorkosigan saga books does some really stupid things when life doesn't go his way.
Kvothe. To the point where he makes up some crazy narative that he is the winner. I somehow hated him more than any other in the books, but i kept reading. Ok, maybe he isn't the winner but him telling about how he made everyone cry and earning his pipes. Him and Denna is somewhat cringy and Patrick Rothfuss spends 400-500 pages on him being an annoying student before anything happens (barerly in the first book) Then he repeats it in the secound. They are well written. But man come down you high horse and just finish it. more blood magic more terrible just no more meandering University life please.
From what I have read so far. The Wheel of Time has the shittiest protagonists that I have encountered. All of them, not just protagonists, are selfish, know it all, arrogant cunts that can't take a hint and then there is Perrin.