American enslavement was the worst, because we are the only people that de-humanized human beings. Denying people were people and acting on that denial was inhuman.
Only animals treat people like animals. Even now, white Americans are still struggling to come to terms with the fact, that their ancestors were animals. Animals in human form, but animals nonetheless.
Slaves acted like human beings — not animals. Enslavers did everything they could to beat humanity out of slaves — and failed. No matter what the enslaver animals did, slaves held onto their humanity — they formed families and friendships and prayed to their G-d. They comforted one another and offered compassion and understanding. They kept each other strong and kept their humanity alive.