This ending would happen, of Lucas didn't tell Y/N, that they are going to check his house.
Your POV:
Me and Kyung-Mi were sitting on the sofa and watching a movie. Suddenly, we have heard somebody knocking on the door. I told Kyung-Mi to hide under a sofa and I openned the door. My brother was standing there with group of MTFs. Does he work for them?
You: Hey Lucas, what happened?
Lucas: Good to see you Y/N! We need to check your house.
You: Uhm, did something happen?
Lucas: Yea, but don't worry, start searching guys, but I am almost sure, that he is clear.
They started walking around my house. Are they looking for her?
You: Uhm, but tell me, why are you doing all of this?
Lucas: Well, you see...
Suddenly, I have heard gunshots from the living room. Kyung-Mi was running away in her fox form and hid behind me.
You: ... Don't you dare to touch her...
Lucas: Y/N, calm down, don't worry, everything will be fine...
You: I won't let you hurt her!
Lucas: ... I didn't expect that you will be under her control... I am sorry Y/N...
I have felt something hitting my leg. I fell on the ground.
Lucas: Fire.
I wanted to scream, but I was too weak. My vission became blurred.
Lucas: Don't worry Y/N, when you wake up, you won't remember about that. You are safe now...
I lost my consciousness.
I woke up in my bed. My head hurt, and I didn't remember anything. Did I get drunk? I checked my diary to see, if I wrote something about that. I was shocked. I saw many pages written about something, I didn't remember. What happened? I couldn't remember anything. I have decided to check cameras. I saw myself with a woman, I don't remember. This cannot be fake. Something must have happened. I continued checking the cameras. I was speechless. The Foundation was real. I was in love with Kyung-Mi, also known as SCP-953 and they have killed her, and amnesticated me. Lucas... You little piece of shit! You and your Foundation will pay for that!
I went to my computer. I knew how to hack, but I didn't have a reason to do that. I activated my own VPN and started hacking. After four hours, I had access to all nuclear weapons in this world, even the ones owned by Foundation. What's more, nobody noticed. I didn't waste time and activated them.
Amount of nukes armed: 11 816.
Target: Every square kilometer on this planet.
I pressed enter and sent all nukes. You wanted to save humanity?! Good luck now! SCP-2000 won't save you, I have sent enough nukes there to make Yellowstone supervolcano erupt and destroy everything. I had to wait 160 second. This is for all SCPs, this is for you Kyung-Mi.
120 seconds. I have heard somebody knocking on my door. I went to my bedroom, openned the safe and took my guns. It is too late to stop that anyway. MTFs and my brother rushed through the door and ran after me. I began shooting at them. I have killed all of them except Lucas. I have attacked him and put my gun to his forehead. 83 seconds.
Lucas: Brother, why? Why do you want to kill everyone?!
You: You took away my true love, you took Kyung-Mi away from me. You all deserve to die, she was the only reason, why I didn't kill myself, and now, when she is gone... I will take all of you with me.
Lucas: Brother, you are insane! You want to kill 8 billion people?!
You: Yes. None of you will survive. You should have thought about consequences, when I told you, that I won't allow you to kill her.
Lucas: But... But we amnesticated you!
You: I had a diary and cameras in my house. 38 seconds.
Lucas: O5s, what should we do?!
You: You have a radio with you? Perfect. Listen O5s, this is your punishment for giving a termination order for SCP-953.
O5-1: B-But we never did that.
You: Don't lie to me! 21 seconds. You all will die!
O5-1: ... Something is not right. Bright, you are our last hope. Lets pray that SCP-963 survives that.
You: Even if it does, I doubt that there are aliens. 12 seconds.
O5-2: If I come back to live, I will save us, don't worry.
You: 5, 4, 3, 2, 1...
I saw a giant explosion, and I didn't feel anything anymore.
The end?