Every date is made by joining two Karana. There are only 11 Karana. Out of which Bava, Balva, Kaulava, Taitila, Gar, Vanija, Vishti are Char Karana and Shakuni, Chatuspada, Naga and Kinstughan are constant or Dhurv Karana. So Vishti Karna is comes in a category of Char Karana. Vishti Karana is a malefic (Paap), moving Karana, ruler of this Karana is deity Yama, who's responsible for death matters. Shani (Saturn) is Graha, who's ruling Vishti.
Vishti Karana that is also known as Bhadra Karana in Astrology, thats why it is avoided in mostly all auspicious activities and events. Vishti Karana is not considered as an Auspicious or Fortunate Karana in astrology. The person born in this pericular Karana may be influenced by the maleficent Vishti Karana. He may have very suspicious nature and may be associated with some immoral activities.
Vishti Karana effect the person with its negative nature by which the native might have a distrustful character and may be attracted towards other women. He may go to any extent for revenge. Vishti Karana is also appropriate for the person to involve in destructive activities like kidnapping, killing someone, war, igniting fire, poisoning, destruction of enemies, harming with Tandiva acts etc.