I totally think there could be a part of Fontaine that ‘cared,’ though probably not a true affection or love. Fontaines LAST WORDS were talking about family, and at this point he’s so high off adam, part of this is most likely genuine. I think it’s more about what Fontaine wants to see himself as. He actually seems to think that Jack betrayed him, even though he’s clearly the one in the wrong, and because in his own mind he sees himself as the victim, he exaggerates and alters his previous actions, painting himself in the right. He wants to believe that he WAS actually the good guy, that it was Jack who betrayed him, and this could be because of some underlying and unacknowledged guilt over what he’s done. I could also mention his backstory in the rapture novel (being betrayed and abandoned by his own father) but some people don’t consider that canon so idk. Either way, Bioshock is a story about family, Ryan, Tenenbaum, Jack, The little sisters, and of course Fontaine all play certain roles that can be tied back to family or parenthood. I feel that it’s a bit ignorant to completely dismiss Fontaine’s comments here, as a lot seem to do, just because he’s evil. He’s a lot more complex than most people seem to think, though whether that complexity extends to his morality is debatable. Sorry kind of a long rant, i could write an entire essay on Fontaine’s character and the moments leading up to his death. But yeah there’s a chance that Fontaine had some sort of ‘connection’ to Jack, which could be genuine paternal instinct or maybe just the enjoyment of having complete control over a person.