Here is how Nighlock interrogates Dark Eagle and Twilight Sparkle kills him in the opening of My Little Pony Injustice: Gods Among Us.
[we see a quote from Lex Luthor saying "I can say without a doubt that there are an infinite number of universes. Some are much like our own... But for one or two occasions, exactly the same."]
[We see Canterlot in ruins. We see a news report saying Canterlot Destroyed. Millions Dead. We see cops from Ponyville running to deal with the situation while others look on in shock and sadness]
[We then hear Dark eagle laughing maniacally. We see he is being interrogated by Nighlock]
Nighlock: [angrily] [slams his hand on the table] The nuke, where'd you get it?
Dark Eagle: Why, you want one? [jeers] Copy mutant.
Nighlock: [yells in rage to slam him on the table]
[Suddenly, the wall bursts open as Dark Eagle chuckles evilly. Twilight flies in, her eyes glowing with dark magic and rage]
Twilight Sparkle: GET AWAY FROM HIM!
Nighlock: I'm handling this.
[Twilight walks up to the table and tosses it against the wall in anger then picks Dark Eagle up with her magic and slams him against the interrogation window, cracking it a little]
Twilight Sparkle: [angrily] YOU DRUGGED ME! MADE ME- [sadly] Flash. My daughter.
Dark Eagle: First Ponyville. Now Canterlot. The ponies you love tend to blow up around you, don't they?
Twilight Sparkle: [raises her hoof in rage to punch him]
Nighlock: Twilight, don't!
[Twilight punches the glass instead, cracking it a little more. She then hung her head in sadness as Dark Eagle chuckled]
Dark Eagle: Heh. [puts his hand on her shoulder] That's why I like you, Twilight. You're much more gullible than. [gestures his head at Nighlock]
Twilight Sparkle: [tosses him across the room]
[Dark Eagle lands on the table and breaks it on impact. He gets back up and puts his hand on his back, which clearly sore as it pops]
Dark Eagle: You think you can have a family. That locking me up will somehow magically reform me, or the Element of Harmony will somehow magically reform me. That they'll be safe. [picks up a chair and sit down] So big. [flexs his muscles] So dumb. [touches his fingers to his head and removes them]
[Twilight slowly walks towards him]
Dark Eagle: Now run along so I can break out of here. I've got lots of planning to do to top this.
Twilight Sparkle: [in rage, grabs him by the throat and weakens his armor a little with her magic]
Nighlock: That's enough!
[Twilight pushes him aside as Dark Eagle realizes what's coming as he had planned for it]
Dark Eagle: [weakly] I know it's soon, but... Think you'll ever love again? Maybe you won't kill your next family...
[Twilight had had enough and thrust her hoof through Dark Eagle's chest while Dark Eagle screams in pain and laughter as Nighlock watches in horror.]
[But worse, as his original foe fell to the ground, dead, Nighlock knew this was just the beginning. Dark Eagle was gone. And so was his fellow leader of the Equestrian Avengers]
[And his prediction was right. Over time, Twilight slowly but surely became a killer. When Twilight's parents were kidnapped by Mirror Master, Twilight recruited Thomas, Taser, Rainbow Dash, Quicksilver, Rarity, Living Lightning, Applejack, Vision, Starlight Glimmer, Red Smoke, Fluttershy, Scarlet Witch, Knightwing, and Archangel to her cause. After dropping the Crystal Empire in the middle of the Badlands, Twilight continued to go even darker. Later, Nighlock was ousted from the Equestrian Avengers]
[We see Nighlock and his adopted daughter, Kaitlin aka Sprite III, flying through Ponyville,
[MY LITTLE PONY INJUSTICE: GODS AMONG US appears on the screen]