It's not like Benedict can say he didn't expect retribution, but he still gasps in alarm when it comes, his leg buckling as the rest of him crumples to the floor.
The kick is solid, but not solid enough to be felt too clearly through the adrenaline now surging through Benedict, which has him back on his feet in moments and whirling on Matthias to stride forward and give him a good shove.

"You fuck off!" he snarls, mindless of the foolishness of the moment, of how unlikely it is he'll beat Matthias in any sort of physical altercation.
If he had a moment to think about it, he'd likely chalk it up to this being worlds better than attending to their miserable surroundings.