The thread of least comfortable looking chairs  

That's a tough one to beat.
I offer Jonas Bohlin's Concrete chair. It's Swedish.

Mr. Reitveld
Nothing says comfort like an acute angle cutting the back of your knees.

And Newsome too
I think this would be especially apt if left in the sun for a few hours on a bright day.

Love that one. . .
I don't know how one would even stay on the thing ! Would make a nice prop for movie like, oh, Dune, maybe . . .?

I give you
the Steltman chair, and the Berlin chair, of G Rietveld.
Boy, we're picking on that guy !
Frank Lloyd Wright is next. . .

(Nice
graphic display, huh ? Came out better than I could have hoped !)

The pencil chair.... and a...
The pencil chair.... and a list of twelve more frightening designs.
http://weburbanist.com/2009/10/11/oh-sit-the-worlds-13-most-uncomfortabl...

stainless steel bean bag
They had to move these out of the gallery near me because people were hurting themselves sitting in them.
fm

Ekstrem

Gruppo Strum's Pratone chair...
Gruppo Strum's Pratone chair always looked rather uncomfortable to me.

Michele de Lucchi's "First" for Memphis

Psuedo Spanish Horrors
I sat on these chairs athe dcar dealership yesterday whilst waiting for a tire puncture to get repaired. They,like a lot of stuff out here in Santa Fe, are psuedo Spanish. I wish I'd thought to take a pix with my phone. But besides being totally fugly, they had a completely flat seat and the back was at a perfect 90 degree angle to the seat and also unforgivingly flat. I thinkk that's got to be the worst and most uncomfortable design for a chair. We are not flat, nor to be bend at perfect angles.