Jon sees a murdered family for the first time and just breaks into tears at the sight.
Superman #39 (Super Sons of Tomorrow Part 4)
Jon sees his father trapped in Red Kryptonite and desperately pounds at the glass while Superman continues to grow weaker. Jon has to be held back by Starfire, Kid Flash, and Damian even after being weakened by Kryptonite exposure before finally losing it when his father seemingly dies.
Jon: I'm confused...these guys are scared to death of you. Exactly how many people have you...killed? Damian: (not looking at him) First, let's clarify that these people were killers themselves. And that was a whole other lifetime ago. Jon: You're thirteen.