Mistress vs Slave: (female mc) Orc Captive Route (1.81) has your character as a slave to an female orc chieftan. Technically starts in the middle of the story and you'll have to play default route (1.09) to get the full context. But it jumps you to directly after being caught.
Master vs Slave: (female mc) You play as a slave in this one. Don't remember the specifics but it was a decent game.
Karlson's Gambit: (male MC) Not an exact matcch. VN with more of a story focus. But your character (male) is a slave from the beginning.
Broken Dreams Correctional Center: (choice mc) You are a prisoner. Somewhat similar to Lilith's throne in gameplay
Adventures of Garnet: (female mc) Old RPGM game. Has a couple of routes that end with you as a slave.
Perverted Education: (male mc) Focus of feminization and chastity. MC isn't actually a slave but the game has you being given tasks to complete so it does sort of fit.
Missy: (female mc) At least one route has you become slave to the bullies.
Death's punishment: (female mc) Has you start as a slave and you can continue as a one (by submitting to others) even if you escape from it.
A New Dawn: (female mc) You can end up as a slave in the Orc city. Has a lot of sub/corruption content though.
Lona RPG: (female mc) You can end up as a slave in a couple of routes
Cursed Armour: (female mc) Has quite a few routes where you end up a slave. Of note is one where you are officially one in a slave city. Great game over all
Cursed Armour II: (female mc) Same as above. Lots of such content and also has the same city as a major route.
Harshville: (male mc) I think it has an official slave path but you have to earn money on the regular and the gameplay loop fits.
Degrees of Lewdity: (choice mc) Has a
lot of paths where you end up a slave.
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: (female mc) Has at least one route where you end up a slave to a blackmailer. Lots of similar type content.
Magician of Olecta Desert: (female mc) Has defeat routes that have a full slave gameplay. Look up other games by the same dev. Pretty sure they have the same idea with slave loops too.
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: (female mc) You can end up a slave in a couple of paths including one with the villains.
Enslavement war: (male mc) You are a slave owner who can end up working as a slave in his home.
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: (choice mc) Similar to Lilith's Throne. Also look at the Corruption of Champions on the same site. Don't remember if any of these have full slave routes though.
Kingdom of Deception: (female mc) You are a captive of an orc tribe. Has slave routes.
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(female mc) All the games there are about you being or becoming a slave.
SlutCraft: (female mc) You are a slave being trained.