Let me elaborate then. Yes, Barty Crouch Snr did not spend much time with his son, Barty Crouch Jnr, but the imperious curse was not used until long after his involvement with the dark lord, yes I am a death eater, in-fact, it was after he was sentenced to imprisonment in the Longbottom case.

also, your point of 'after having a father like BCS...' I think it is being blown out of proportion. As I mentioned previously, he was busy, and thus could not pay a lot of attention to his son. That is it. I did, in order to not be wrong when I am presenting a counterargument, go through his fandom wiki, and I think it has my back. He joined the death eaters when he was a teenager, and he was one of only two death eaters to remain, even Bella was gone, although through imprisonment. Yeah, that's it, just the part where you mentioned his relations with his father, that is where I found the problem. Thank you again!

Also, I think he might have a part in him that wants to see Neville shiver as he mentions the curses, not only, if, to console him. Sorry, it is long...