The most audacious/risky debut album

For me, I'd have to say Boris did with Absolutego. That they started with dark, fuzzy and low-fi drone doom that gives your speakers an unprecedented workout, and that it was one hour long track with fifteen minutes of squealing feedback at the end, I'd say that's about as risky a career starter as you can get. Yet, look at them now. By the way, Absolutego is still possibly my favorite album from them, but it's a very specific taste.

I just went back and relistened to Corrupted's (also Japanese like Boris) Paso Inferior, and I'll include that as an honorable mention. Any band that sings in guttural spanish while being Japanese and playing a 41 minute sonic dirge of feedback and heavy as heavy gets sludge is definitely making a niche effort.