Kamada Ekadasi vrata, Chaitra Shukla Paksha Ekadashi, removes all the sins including Brahma hathya papam.
The legend or the Vrat katha of Kamada Ekadasi is mentioned in the Varaha Purana as a conversation between Lord Krishna and King Yudhistira.
Once, a Gandharva called Lalita was married to a beautiful woman. After his marriage, he was unable to do his regular works or duties with dedication because of his attraction towards his wife.
Pundarika, the King of Gandharvas realized the fact and cursed him to become a cannibal. Gandharva with his wife wandered many holy places toget rid of the curse.
While they were passing by an Ashrama (hermitage), they met a Sage and asked about a remedy to get rid of their curse. That Sage advised them to perform the rituals and customs associated with Kamada Ekadashi. He suggested them the only and ultimate remedy toget rid of any sin or curse is Ekadasi fasting.
As suggested by the Sage, the Gandharva couple observed the Kamada Ekadasi fasting and got rid of the Gandharvas curse.