Sorry, you can't write Portal2 by using soft bodies :-). You will not get adequate performance - unless your "bullet" is moving quite slowly. Just use an oblate sphere and make the collider smaller than the visual sphere so it seems to deform before it splatters. Or make it actually deform with a bit of scaling trickery.

Lots of Game Physics is just trickery like this.

Thank you so much very clever with portal reference yeah I'm gonna get a lot of that actually its an experiment to see how far I can push the physics but thanks anyway I shall try it and no I'm not creating Portal 2.

I just though of this idea so I'm not sure how well it would work, but... Create a sphere(ish) mesh, with its origin at the center and create bones at uniform intervals on the outside skin of the mesh so that vertices are weighted to nearby bones (more than one bone per vertex) by there radial distance. Then bring it into Unity and apply a sphere collider and rigidbody to all the outside bones. Connect them to the sphere mesh with spring colliders, make a script for all the bones to always have the same constant local rotation that they had when the game started. Then make all that a prefab that gets shot.

As far as an easy and elegant way? I don't think there is one for colliding softbodies in Unity.