There were many anime works where the male protagonist got angry and turned into an awakened character.
Naruto Uzumaki in Naruto: When threatened or challenged, Naruto will show strong willpower and anger, transforming into a Nine-Tailed Fox to achieve his powerful goal.
Fliesa in Dragon Ball: As a cosmic pirate, Fliesa has super strength. When he feels angry, he will transform into a "Fliesa Lion" to show unparalleled strength.
3. Monchi D. Luffy in One Piece: When threatened or challenged, Luffy will show strong willpower and anger, transforming into a rubber man to obtain more powerful abilities.
4. Shizuka Juushirou in Gintama: Shizuka Juushirou is a ronin. When he feels angry or dissatisfied, he will transform from an ordinary ronin into a "ghost cut" and become a powerful warrior.
The transformation and awakening of these characters were based on their anger and challenge, thus revealing more powerful abilities and strength.
The Furious Snail was the name of a novel, and the God of Myriad Realms was the name of an anime. There was no direct connection between these two names. However, the Myriad World God Lord was also used as a fictional character name in some online novels.
Since I'm not familiar with this novel, it's possible that there are prophets or seers as main characters. They could be the ones trying to understand the gods' anger and communicate it to others. Or perhaps there are brave warriors who are either trying to fight against the wrath of the gods or are on a quest to make the gods calm down.
There could be original characters created specifically for this fanfic. These new characters might be the source of Sakura's anger. For instance, a new villain who has targeted Sakura or her loved ones. Or it could be a rival who constantly undermines Sakura, causing her to be angry. Additionally, characters from other related series might make cameo appearances if it's a crossover - type fanfic.
The main character is the 'last angry man' himself. Around him, there could be family members such as a wife or children who either support or are at odds with his angry nature. There may be neighbors who are affected by his actions or words. And perhaps there are colleagues or people from his workplace if the story has that aspect. There could also be a local community figure, like a priest or a community leader, who tries to mediate or influence the angry man's situation.
One character that could work well with an angry Loki is Doctor Strange. Strange is used to dealing with powerful and unpredictable entities. He could either try to manipulate Loki's anger for his own purposes or try to help Loki come to terms with it. And of course, Sif. She has a history with Loki and her loyalty to Asgard could put her at odds with an angry Loki.
I don't have enough information to say who the main characters are. It could be a tough - as - nails Aussie bloke who's had a rough life and is out for revenge. Or maybe a group of characters, like a gang of outcasts in an Australian town.
Batman's allies such as Commissioner Gordon could be involved. Sometimes Batman might be angry at Gordon if he feels that the police force is not doing enough to support his fight against crime. Also, other members of the Bat - family like Batgirl could be part of the story. Their actions or decisions might trigger Batman's anger. For instance, if Batgirl decides to take on a powerful villain alone against Batman's advice.
Obviously, Italy itself would be the main character. There could also be other European countries like France and Germany. They might be the ones causing Italy's anger, or they could be Italy's allies trying to calm it down.