ff7, remake, and rebirth

most ratchet games, but most notably going commando and deadlocked (the latter being just one big tournament)

There's a tournament arc in the first Trails in the Sky! I think it's pretty common in the Trails series, but that's the only one I've played and can confirm firsthand.

Self-parody moment but I gotta say it: arena progress, appropriately, is required for the story in Armored Core: Master of Arena.

Dragon Quest 4, SMT Nocturne, Live A Live

Would the forced gladiator fight in Ys Seven count?

Super Paper Mario and Xenogears!

Gladius takes place entirely in an arena. Great list idea!

Mega Man Battle Network 4

Cool theme!
Knights of the old Republic has a gladiator ring segment you have to take part in.
The entirety of Pyre is a fantasy sports league so not sure of it counts.
2nd Gen Pokemon has bug catching tournament, I think you have to participate once but it's been a long while.

Metal Arms Glitch in the system has a whole section where you are forced to fight in an arena.

There’s a few decisions I have to make about Pokémon and/or games that are entirely arenas but I’ve appreciated all the submissions I’ve gotten!

Magic Pengel and Dragon Quest Monsters might fit as well depending on how you decide the criteria. I could see them being a little too gray though since they're not exactly "arcs" (though the pacing is different from something like Pokemon for example)

FE awakening chapter 4. cool idea for a list

Wo Yao Da
Tekken 1, 2, 3, 4, 5, 6, 7 and 8
Like A Dragon Gaiden
Dragon Quest II and VIII
The Witcher 3: Blood and Wine

Breath of Fire 2

Klonoa 2: Dream Champ Tournament (the whole plot)
Lisa: The Painful (the Russian Roulette sequence which you can repeat to higher tiers)
Sonic Riders (most of the plot)

Pokemon Sword and Shield: Most pokemon games have the elite four, but Sword and Shield is the only one with an explicit World Tournament in its main story.

Since Dragon Ball Z: The Legacy of Goku II adapts the Cell Saga, that technically includes a tournament / arena arc.

Summon Night: Swordcraft Story has a tournament arc as a central plot point.

Persona 3: FES has The Answer, where the main characters fighting in an Arena and having to beat the other main characters to get a special key is critical to the plot as a mini-arc.

Technically, any sports game with a playoff system in their Franchise / Career mode would fit this such as Madden or NBA games. But I'll note down LEGO Racers since while super basic, it has a story mode compared to the others.

Pokemon Colosseum specifically forces you to fight in a tournament (the Pyrite Cup) as part of the plot, and both it and Pokemon XD force you to fight in Mt. Battle at least once (which is more of an arena style deal).

The original Street Fighter's only mode is a tournament. Street Fighter II's Arcade (and thus story) mode is Bison setting up a tournament to try and brainwash the strongest fighter.

Radiata Stories begins with knight selection trials, which are a tournament / arena bit. You only get to fight in one battle but there's a tournament roster shown and it takes place IN an arena and everything. And is mentioned as a tournament in dialogue.

Radiant Historia has a Coliseum Arc

starting that 700 page gamefaqs thread i don’t remember the meme shadow of the colossus

- Mega Man Battle Network 3: A surprising amount of the early-to-midgame consists of progressive stages of an event called the N1 Grand Prix, intended to find the country's top NetBattler. Later in the game, MegaMan must find and defeat most of the Undernet's strongest fighters in order to obtain a program crucial for shutting down an incoming threat to the Internet and society at large.
- Jimmy and the Pulsating Mass: The King of Everchip stages a single-elimination tournament in an attempt to get rid of Jimmy, whom his evil chancellor loathes utterly. Jimmy, his mom, his uncle, and a lot of other characters are imprisoned and forced to participate.
- Custom Robo: Battle Revolution (subtitle optional, it's the Gamecube one) and Custom Robo: Arena : it would probably be easier explaining the parts of these games that are NOT tournament arcs
- .hack//G.U.: Volumes 1, 2, and 3 each have one; in all three it's because it's the most reliable way to get in contact with one or more significant characters that just so happen to be PVP champions.
- Octopath Traveler 1: One of Olberic's chapters involves a tournament in Victor's Hollow.
- Guilty Gear (but only the first one/The Missing Link)
- Pyre (Supergiant Games): At least, I assume the Rites are overall laid out in some kind of structure...? This one I might just be wrong about.

OG Mortal Kombat, MK9, and Mortal Kombat 1, every Fatal Fury and King of Fighters game.

Lightning Returns

Kingdom Hearts I and II

Street Fighter 6 has multiple instances

Bug fables has a small arena section that’s required for the story

I had no idea just how common this trope is... Awesome list!

Tales of Vesperia requires you to do a quick tournament in the Nordopolica coliseum in order to advance the plot.

- Kingdom Hearts Birth by Sleep
- Pokemon Battle Revolution (Stadium games as well I believe?)
- Yakuza 0
- Yakuza/Yakuza Kiwami
- Paper Mario TTYD Remake
- Star Ocean 2 and its remake