Question Unity adding background to transparent image, please help

In the above images you can see 3 nearly identical textures with the main difference being the first texture contains a black background, the second and third do not as the background is hidden in photoshop before exporting. The problem is I can use the first image with an Unlit shader in Unity using an additive blend mode and it will hide the black but for the second two images Unity automatically creates a background and I'm unable to remove.

Here is another view to show the alpha channels of the 3 textures:


Here is an example of what happens when I switch the blend mode on the shader for the third texture (the one without a background) from additive to alpha:



Now note, I realize I could just use the additive shader to create the white or colored crack but the point of this is to use a dark black color which does not display in an additive blend mode.

Please assist.