In The Door to Satisfaction, I give the example of a monk of high spiritual attainment who, because he was in great pain, asked his disciple kill him. The disciple then suffocated his master. Because the disciple’s motivation was good, Buddha said that he had created no negative karma, only virtue. However, performing euthanasia with a good motivation is not sufficient, because we need to help others with wisdom as well as compassion.
If the person will have more peace and happiness in their next life, our action is good. On the other hand, even though our action may stop the person’s present suffering, it could result in their being reborn in a realm where their suffering will be a million times worse.
My concern is more for the outcome in the person’s next life. If they are going to reincarnate in a hell realm, for example, it is better to keep them alive one day or even one hour longer. Since we don’t have the clairvoyance to see where the person will be reborn, we have to rely upon the wisdom of fully awakened beings who have omniscience, compassion for all living beings and also the perfect power to guide us.
However, in the case of someone who is going to stay in a coma for many years, rather than spending thousands of dollars keeping them alive, it would be good to use the money to purify their negative karma which will cause them to suffer in their future lives. It would be better to spend the money benefiting many people and then dedicate the positive energy created not only to the temporary happiness of that person, but to their liberation from all suffering and achievement of enlightenment. Giving the money to a good cause is the best thing to do. It can be done on behalf of a family member, a friend or even an enemy and can help to relieve feelings of guilt.
Whether the person is still alive or has already died, it is best to purify their negative karma. This help can come from family members and friends. Helping others with wisdom and compassion in this way makes it meaningful for us to have met, known and lived with them.