That’s an earlier Marder. A picture of the current marder is in post #3.
Those marders were Tank Hunters. Panzerjagers I believe is the German for it. They would lay in wait for a unsupecting Sherman or T34 and ambush them. They were lightly armored, so they couldnt go toe to toe, relying more on hitting them from the side from cover.
Now, if you want to talk about killer tanks, lets talk Panther.