I get that, but... Predominantly different viewpoints just doesn't work for me as a *realistic* motive to murder your sister's child whom you have gone to great lengths to save. At least not as a first move, without even trying to defeat him non-lethally first.

I mean, just off the top of my head, Talia (before they turned her into a total villain) and Ra's al Ghul also had completely different goals at times and even went so far as to openly fight each other, but Ra's always did everything he could to beat her without killing her. Same with Deathstroke and Cassandra. Mystique and Rogue. Magneto and Xavier. Even Loki was extremely reluctant to kill Odin, usually leaving it as a last resort.

I could buy that eventually, after trying at length and continuously failing to get his nephew to either support him or at least not getting in his way, Adam might snap and kill the kid. But like 5 minutes after getting rescued by the kid, from a wound Adam got because he fought so hard to save the kid, when said kid is the only family he has left and is hugging Adam while telling him how much he loves him and begging him not to resent him?

No. I hope it's just a red herring, because if Adam really did murder him that's bad writing.