Ultrafast laser pulses at mid-infrared wavelengths (2-20 μm) interact strongly with molecules due to the resonance with their vibration modes. This enables their application in frequency comb-based sensing and laser tissue surgery. Fiber lasers are ideal to achieve these pulses, as they are compact, stable, and efficient. We extend the performance of these lasers with the production of 6.4 kW at a wavelength of 2.8 μm with complete electric field retrieval using frequency-resolved optical gating techniques. Contrary to the problems associated with achieving a high average power, fluoride fibers have now shown the capability of operating in the ultrafast, high-peak-power regime.