Endless
The Dark Zephyr had crossed an enormous distance in a short amount of time. Its speed wasn't as blazing as other expert mechs, but its skillful expert pilot and its emphasis on evasion allowed it to start its end run without suffering any crippling damage.
Many other expert mechs would have been torn to pieces by the Gauss Baron by now! It was a massive accomplishment for Venerable Tusa to get this close to a hostile expert heavy artillery mech by relying mostly on itself.
However, the hardest part came last. Not only did the Dark Zephyr have to bypass or fight through a horde of dwarven escort mechs, but it also had to find a way to get past the heavily-armored bunker that had taken an enormous beating but still remained fully intact.
Then, Venerable Tusa had to attack the Gauss Baron itself, and he seriously doubted that the expert heavy artillery mech would just roll over and allow itself to get butchered by a human expert mech.