[lentulusgracchus]

Do you think the Lincoln assassination was a "positive good"?

No, it elevated Lincoln into the American pantheon and terminated all rational discussion of his policies and constitutional pretensions. Had he lived, there would have been some sort of reaction against what he did to the country. His death and monumentalization arrested that.

[fortheDeclaration]

No, had Lincoln lived he would have prevented some of the worst abuses of Reconstruction.

The worst thing that could have happened for the South was Lincoln's death.

[capitan_refugio]

"Had [Lincoln] lived, there would have been some sort of reaction against what he did to the country."

Rank speculation on your part. What is more likely is that Lincoln would have kept the more radical reconstructionists in check, and the "heaven-sent" (to use your terminology) actor John Wilkes Booth would have been littel remembered.