dreemurr | CHARACTER NOTES.

just some notes on my interpretation and depiction of Chara, since they're a vague character in what we're given within the game. warning for mentions of suicide and child abuse.

They suffered abuse at the hands of their guardians in the village, and were similarly mistreated and ostracised by others there. (Chara... hated humanity.)
Fleeing to Mt. Ebott was an attempted suicide. (The only thing said about it is that humans don't return, and that carries an implication of death more than anything else. Why would you climb a mountain like that? ... I know why Chara climbed the mountain. It wasn't for a very happy reason.)
Although unexpected, their relationship with the Dreemurrs was genuine; they loved their family and were loved in return. (The Dreemurrs clearly cared about Chara themselves. There are items that stand out as sentimental for Chara: the macaroni art they made, the heart locket that matches Asriel's — Right where it belongs. In the picture of the family, "everyone is smiling".)
On Chara's intentions with the buttercup poisoning: they had more than one reason for this. They wanted to free the monsters from the underground. They wanted revenge on the people of their village — whether they consciously acknowledge this or not, their actions on the surface speak for themselves. They didn't really see any hope of recovery or redemption for themselves, no future to speak of, and so they chose to give up their own life; a slow, painful suicide that Toriel and Asgore wouldn't be able to stop.
They're a messed up kid. Most importantly, they are hurt, and angry, and miserable. They aren't simply "a bad person", but they're manipulative and were willing to slaughter humans because of the hurt done to them.
Chara is a mirror to Frisk. In a Pacifist Run, Frisk heals from whatever brought them to Mt. Ebott in the first place; their hurt leads them to be soft and kind to others and they find their reason to live in love. But Chara's hurt turns to anger and bitterness and violence, their reason to live is their hatred and their desire to make others hurt too, they never recover like Frisk did. They loved and were loved, but it wasn't enough to save them.
The "Chara" encountered at the end of a player's No Mercy Run is not the same as the Chara that lived with Asriel. It's a remnant from their violent death, a vengeful soulless shade that is revived and guided by the actions and decisions of a Merciless Frisk until it becomes an independent being and takes over.
Chara as I play them has never gotten to the end of a No Mercy Run. They're either immediately post-death, or got most of the way through a No Mercy Run (up to Sans' fight) before there was a reset followed by a Pacifist Run/True Ending.