In the House of Healing found within the Shadow-Cursed Lands of Act II, you will find Malus Thorm and 4 sisters performing surgery upon a helpless victim within an operating theatre. To get this achievement combat must be initiated, so convincing him to allow the sisters to perform surgery on himself, thereby killing him, will not work. In combat, the sisters can stun and hold party members allowing Thorm to perform surgery, therefore it is best to eliminate them first, preferably before entering combat by convincing Thorm that the sisters need to improve their surgical skills on one another. During combat, Thorm will resurrect the sisters by touching them, so holding or immobilizing Thorm is a good strategy.