A buddy has a mixed Jadgterrier and Airdale, maybe 20-25 lbs. I watched it kill a 45 lb. Roe doe in seconds. For some reason the Doe decided to hide instead of run, maybe she had a fawn nearby. We looked for the fawn until well after dark and never found or heard anything.
Another buddy turned his two Jagdterreirs loose in a stack of Hay rolls. The farmer had been complaining that the Cows refused to eat the Hay because it was full of Fox scat and urine. Fox are notorious for being able to navigate through small openings and most dogs can't follow because their chest is too deep. Jadgtterriers are bred for this. One Terrier latched onto a Fox, the second Terrier in its excitement latched onto the first Terrier. We pulled the whole bunch out of the Hay rolls still latched onto each other. We had to use a stick to get the jaws open on both Terriers to get them to release.
Pound for pound Jagtterriers are ferrous little dogs, kind of the Wolverine of the dog world.