Cordelia

Cordelia was an abusive and promiscuous woman who would use anyone, including her own children, in order to be acknowledged by her husband. She is shown to be very manipulative, seeing as how she was able to convince Richter that she would make him the leader of the vampires if he resurrected her.

She is also a very cocky and arrogant person, who believes everything should work in her favor. She doesn't react well when things go against her wishes and with that arrogance, she does everything to get what she wants and would not hesitate to hurt her children or the other mothers.

In addition to this, she was also very strict and abusive to her children. She is commonly known to be the very woman who caused mental (and physical) damage to the triplets. Cordelia is also very flirty. She often flirts in front of the triplets and even goes as far as to having sexual affairs in their presence. It is also revealed that she really didn't want to have children in the first place.

(Source: Diabolik Lovers Wikia)