In this Letter, we demonstrate a single-stage erbium-doped fluoride fiber amplifier composed of two spliced large core fibers with respective diameters of 85 and 130 µm. An optical parametric generator (OPG) operating at a 5 kHz repetition rate, and providing ∼2 ns pulse duration, and an average output power of 500 mW at a wavelength of 2.8 µm was used as a seed source. This nanosecond amplifier configuration achieved an average output power of 10 W with a record pulse energy of 2 mJ, corresponding to 1 MW of output peak power. The maximum slope efficiency of this hybrid amplifier is 21% with respect to the total incident pump power at 940 nm. The presented master-oscillator power-amplifier (MOPA) configuration shows its potential for further power and energy scaling.