Lich/Sister killer, prime the [Galvanized Hell] and merciless with enemies or thralls before fighting.
Prime the [Motus Setup] for more critical chance fire the alt fire.

Corrosive is the MVP here, armor on liches and corpus sisters are ferrite armor, meaning that corrosive strips it away.
You could change out [Contagious Spread] if you have a riven because the weapon will still have the innate toxin lich bonus.