Given the question: What was the last name of the person who used a powerful amplifier in Foo Fighters songs?  Answer the above question based on the context below:  Grunge is generally characterized by a sludgy electric guitar sound with a "thick" middle register and rolled-off treble tone and a high level of distortion and fuzz, typically created with small 1970s-style stompbox pedals, with some guitarists chaining several fuzz pedals together and plugging them into a tube amplifier and speaker cabinet. Grunge guitarists use very loud Marshall guitar amplifiers  and some used powerful Mesa-Boogie amplifiers, including Kurt Cobain and Dave Grohl (the latter in early, grunge-oriented Foo Fighters songs ). Grunge has been called the rock genre with the most "lugubrious sound"; the use of heavy distortion and loud amps has been compared to a massive "buildup of sonic fog". or even dismissed as "noise" by one critic. As with metal and punk, a key part of grunge's sound is very distorted power chords played on the electric guitar.Whereas metal guitarists' overdriven sound generally comes from a combination of overdriven amplifiers and distortion pedals, grunge guitarists typically got all of their "dirty" sound from overdrive and fuzz pedals, with the amp just used to make the sound louder. Grunge guitarists tended to use the Fender Twin Reverb and the Fender Champion 100 combo amps (Cobain used both of these amps). The use of pedals by grunge guitarists was a move away from the expensive, studio-grade rackmount effects units used in other rock genres. The positive way that grunge bands viewed stompbox pedals can be seen in Mudhoney's use of the name of two overdrive pedals, the Univox Super-Fuzz and the Big Muff, in the title of their "debut EP Superfuzz Bigmuff".  In the song Mudride, the band's guitars were said to have "growled malevolently" through its "Cro-magnon slog".
The answer is:
Grohl