Bete Noire's pet Akumu and her pink blob monsters kill people by violently stabbing out their souls and then consuming them.
Though it's not worse than a TV-14 rated show, the series nonetheless doesn't hesitate with blood and violence.
In Episode 7 Season 2 , A character is badly beaten up by his own wife, but he presumably survives.
In Season 1 Episode 4, a character had his arm ripped off.
In Episode 3 season 1, Chara cut off his own arm.
Frisk, the main protagonist, get killed multiple time by Sans in the first episode.
Season 1 is passive violence, but season 2 is more violent.