Here's a comparison of the number of google hits for "archconservative," "archliberal," "ultraconservative," "ultraliberal," "extremely conservative," and "extremely liberal":

	Conservative	Liberal
Arch-	25,000	3,600
Ultra-	140,000	68,000
Extremely	190,000	100,000

  I assume it will be impossible to reach agreement on why the numbers are unbalanced. Perhaps those on the left will tend to say it's because those on the right are more extreme; presumably those on the right will tend to disagree, and will tend to say it's because those on the left are more inclined to discredit opponents with dismissive labels. Or maybe it's because those on the right side of the political spectrum are more likely to self-identify as "conservative" than are those on the left side to self-identify as "liberal." I don't know, but it's interesting to me that the numbers are unbalanced. (Or perhaps I'm just missing other prefixes that balance this out? That's a possibility, too.)