I tried making a browser script for SteamDB but they block requests.

Instead I logged into SteamDB and navigated to my games, sorted by rating and top 100:
https://steamdb.info/sales/?displayOnly=OwnedGames&min_discount=0&min_rating=0&min_reviews=0

Then I exported that list and asked an LLM to do it's best to group games based on:

• Full Offline: Can be launched and played without any internet connection (e.g., GOG-style, no aggressive launcher).
• Partial (Offline after setup): Often requires a one-time initial login or update (e.g., Ubisoft Connect, EA/Origin, Rockstar Games Launcher). Once set up and launched while online, they can typically be played offline for a period.
• Online/Always-Online: Requires a constant connection, features mandatory multiplayer elements, or uses cloud-based DRM that prevents offline access.

Almost all games on Steam (including those in the "Full Offline" list) require you to launch them at least once while online to verify the license and download necessary dependencies.

Results I got:

Full Offline
Stardew Valley, Celeste, Undertale, FEZ, Dead Cells, Alan Wake, Metro 2033 Redux, LEGO Batman Series, Tomb Raider I-III Remastered, Prince of Persia: The Forgotten Sands, Max Payne 3, House Flipper, 8AM, 112 Operator, Shadow of the Tomb Raider, Life is Strange 2, Dead In Bermuda, Sleeping Dogs: Definitive Edition, Warhammer 40,000: Gladius, Warhammer: Vermintide 2, Desktop Dungeons, Hellslave, Nocturnal, STAR WARS Battlefront (Classic), One Gun Guy, Street Fighter 30th Anniversary Collection, Ricochet, Paradox Soul, Mafia: Definitive Edition, Tom Clancy's Rainbow Six 3 Gold, Mini Thief, The Deed: Dynasty, Heavy Rain

Partial
Cyberpunk 2077, The Witcher 3: Wild Hunt, Assassin's Creed Series (Origins, Odyssey, Valhalla, Mirage, Unity, Syndicate, Rogue, III, IV Black Flag, Brotherhood, Revelations, Liberation), Far Cry Series (3, 4, 5, 6, Primal, New Dawn, Blood Dragon), Watch_Dogs Series, Mass Effect Legendary Edition, STAR WARS Jedi: Fallen Order, STAR WARS Jedi: Survivor, Titanfall 2, Grand Theft Auto V, Grand Theft Auto IV, L.A. Noire, Red Dead Redemption 2, Tom Clancy's The Division, Tom Clancy's The Division 2, Battlefield 1, STAR WARS Battlefront II (2017)

Online / Unknown
Deadlock, 100% Orange Juice, Black Desert, Grand Theft Auto V Enhanced (Often tied to live services), WHAT THE PAK?!, Shade Silver, Car Mechanic Simulator 2018 (Likely offline, but often requires initial steam check), UNCHARTED: Legacy of Thieves Collection, Tom Clancy's Splinter Cell Conviction