Did anyone else find out about Sans almost killing Frisk before finding out she was his soulmate? Because I don't think Toriel would be happy if she found out. Hell, she might have killed him or forbidden him from coming anywhere near Frisk.
No one ever knew but Frisk and Sans. And he didn’t exactly let himself off the hook, either. He never forgot what a dick he’d been… or how badly he hurt her. He fully expected her not to forgive him, or to want to ever see him. She did though, bless her soft and merciful heart. She understood his anger, and the circumstances that led to his lashing out. How could he have known she was held prisoner by the vengeful spirit of a long dead human? Why wouldn’t he think she was the one that had killed his brother, and had then played innocent? She understood completely.