Is there a way to do this effect/shader?

hi all, i'm trying to do this kind of shader, some kind of blending to background without rendering any object behind the one with this shader, is this possible? i put some screenshots of the effect i want and the effect i have.

first i took this shader from the invaders project of Eric5h5

Shader "Alpha/SelfIllum" {

 Properties {
     _Color ("Color Tint", Color) = (1,1,1,1)
     _MainTex ("SelfIllum Color (RGB) Alpha (A)", 2D) = "white"
 }
 Category {
    Lighting On
    ZWrite Off
    Cull Back
    Blend SrcAlpha OneMinusSrcAlpha
    Tags {Queue=Transparent}
    SubShader {
         Material {
            Emission [_Color]
         }
         Pass {
            SetTexture [_MainTex] {
                   Combine Texture * Primary, Texture * Primary
             }
         }
     } 
 }

}

i tried to modify it without success, this is the effect i have:

and this is the effect i tried to achieve:

is this even possible ? thanks for your answers, basically im trying to do some kind of "fake destructible 2d terrain" as the one in the Eric5h5's invaders project was great but for phone seems to be a bit slowly