Is slavery inherently evil, or justified sometimes and then only bad if your hurting/abusing them?

let me clarify.

im against slavery.

but there is sometimes spiritual and historical debates over sometimes it being more merciful and sometimes culturally its better to be a slave treated right and treated like a person and eventually get freedom

different conditions

American slavery was very evil. this is more about indentured servitude (before leftist get all angry, a lot of modern people are under "slavery" condition by your perspective. and I think its horrible)

Is slavery inherently evil, or justified sometimes and then only bad if your hurting/abusing them?
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