You wouldn't say you're the smartest person in the world, but you're definitely not stupid.
You almost wished that Frisk chose to stay with the monsters, but you wanted them as far away as possible.
After they freed everyone, you unlocked your own memories and theirs of a certain event. You had left them in a 'file' for safe keeping.
You stared down at the photo, and smiled.
It was a picture of your friends, family and yourself. It'd be better with Asriel, but you know that can never happen.
You take your red marker and bring it down on Toriel's face.
You scribble for a few moments, making sure her happy expression is crossed out.
You admired your work for a second, before taking the marker again and scribbling on Papyrus' face.
You continue, moving to Undyne and then Alphys.
The smile on your face grows as you cross out Sans' face. You then go to cross out Asgore's.
You admire your work. In the photo, you have the biggest smile.
Normally, you didn't like having pictures taken, but this time was special. You wanted it to be special for your good friend, Frisk.
You placed the photo side-by-side to your unedited version and grinned.
Smiling, you flipped over Frisk's photo and wrote on the back,
"Greetings, Frisk.
Just wanted to send you this friendly reminder.
Burn in hell.
Best wishes,
Chara Dreemurr."
You hoped it got the message across.
That actions have consequences. That even a true reset cannot erase facts.
That it was them who pushed everything to its edge.
That they made their choice long ago.