Upvote:0
Evil.
No act of sin (however selfless it appears) will ever result in saving or helping another person. There is no question of "balance" here. The long term good outcome from another person will never be the result of someone else having done evil.
See also: Under what conditions can a "good" or "charitable" act actually be sin?
Upvote:3
I think before you can come up with an example scenario, you need an example of a sin that would "result in damnation for the doer."
There is no such sin, since everyone is already deserving of damnation.
And for a Christian who has accepted Christ's forgiveness, there either is no possibility to lose the forgiveness, or the only way to lose the forgiveness is to choose to reject it (depending on your interpretation).
So this might leave room for "Choosing to reject Christ's forgiveness" as a possible sin that would lead to damnation of the doer. But I cannot imagine how this sin could ever be done as a selfless act. So even if it is possible to lose your salvation, it is impossible to it selflessly, or in a way that would save others.
Upvote:5
This whole question is based on a wrong understanding of Christianity and sin; it imagines God as a cosmic traffic cop, letting people into heaven only if they haven't done anything on a hard-and-fast list. In fact that's not the case. God loves his creations - all of them - and wants everyone to be with him in heaven.
Forgiveness is key to Chrstianity, and the central act of God - the crucifixion - was carried out to obtain forgiveness for all people. It goes without saying that forgiveness would be applied to anyone who broke a command for a truly self-sacrificing reason, and they wouldn't therefore receive eternal damnation.
Jesus sums up the law as "Love God, and love your neighbour as yourself." A truly loving act would not be against the law. (I should warn you against trying to take that argument too far, outside the immediate context of this question, though).