That's not their brain, it's called a wen. Their brains are in their skulls like any other fish.
I don't think there are any fish that I particularly can't bear looking at. I admit some goldfish mutations look cruel rather than disgusting (like looking at dyed fish), but I don't think there are any fish I can't bear to look at. Unless you include CAE's, because the only times I've ever seen them they're attacking other fish.