Chara was fully aware Asriel was behind the reset and had become crazy, and they knew Asriel's evil plans of achieving godhood, and erasing the timeline completely had to be stopped, he continues attacking you out of blind rage with his knife, angry about Asriel's actions. This... It's my punishment... My penance... To see what he's become. To fail again and again and again and again and AGAIN... F A T E I S M O C K I N G M E. . .