See this is why I don't think it's fair to compare Kallego with Snape. Snape was just a frustrated incel who yes, was bullied, but decided to be completely bitter about that for the rest of his life, bullied all his students and was overall a terrible teacher. He's a good character but that's about it. He's a horrible teacher and honestly was a complete disservice to Hogwarts.
Meanwhile, Kallego is just the fucking goat. He may be serious and "spiteful" in a way, but he's a great teacher and actually cares about his students. Even when he complained about Iruma, it was never without reason (Like Snape about Harry), since Iruma does fuck up regularly.
Anyway, Kallego is just leagues better than Snape and comparing the two is like comparing an amoeba to a multicellular, conscious and intelligent organism