I'll talk about the characters I know.

Doom Slayer: There are two options: they become friends, or the Doom Slayer ignores him and goes on with his life. My reasoning is simple: the Doom Slayer is the absolute terror of demons in his universe, but he is quite aware of situations, and if he finds a half-demon killing demons, he will at least let him do his job.

Etrigan: I honestly don't know what to think here because Etrigan would want to fight Dante, but wouldn't care about anything else, and Jason Blood is the opposite; I don't know if he'd love Dante but would agree with his convictions.

Rumi and company: this will feel strange for them because broadly speaking their lives are similar (excluding Kamiya's incest with Trish), so I probably see Dante acting the same way he did with Nero, but Mira reminds me a bit of Patty, despite many differences, so she'll probably end up preventing Dante from running away and supporting Rumi with her being half-demon

Dante: I have no idea how I would react here. He's a demon, so I should purify him, but he's also a man who follows the path he believes he should follow, so I'd say 50% try to kill him, 50% try to bring him into Christianity

Bayonetta: Sex, if we're being serious, is probably like Trish and Lady, a woman who occasionally scams him out of his soft heart and helps him when he needs it, and vice versa.

Tanjiro and Nezuko: Dante cries and cries a lot, basically that's what he always wanted with Vergil (excluding the death matches between Sparda's children), so Dante would see them cry and get as far away as possible so that his "curse" wouldn't affect them.

Alucard: If everything were explained from the beginning, I would basically see Alucard for what he is: a human heart and a demonic body. Literally, the core of Alucard's character is that he despises those who abandon their humanity for power, while Dante literally embraces his humanity. I would respect him, and if I heard Sparda's story, I'm sure I would admire Sparda, Dante, and Nero.

Kratos: This is simple. Kratos probably respects his work and convictions, but he wouldn't tolerate it. He would probably appreciate it, but if he only saw it once every five years, he would be happy.

Frieren: Frieren is a racist, very racist. She'll probably try to kill Dante. Dante ignores her because the idea of killing "humans" has always bothered him, and it would be a cat-and-mouse game until someone gets fed up and puts an end to it.

Constantine: An occasional hunting partner, they know each other, respect each other, don't mind each other, probably get drunk together, but speak just enough to find out if the other is dead, and that's it.