bruce killing off a whole army just
>like that and then struggling to murk lil man dont add up.

Well he said that he can remember stuff right after his younger self experiences it.

So he could remember the whole time of bonding with the kid.

Add to that how hard it was for him to cap the other innocent kid.

He just couldn't go through with it.

I'm not saying the movie didn't have massive story problems. Cause it did. But I don't think that's one of them.