What do you call the person in a group who everyone agrees with? Opposite of iconoclast, maybe?

Solution 1:

We settled on "bellwether." It kind of connotes "where you look to see which way the wind is blowing." It sort of hides the "follower" aspect, even though the literal meaning of bellwether has to do with sheep and does connote leader/follower

:-\

I'll leave the question unanswered in case something better comes along.

Solution 2:

Since the word is to have nothing to do with following at all (that excludes words like leader and trendsetter), but could be used after the fact (which also excludes the word bellwether from another answer, since it is normally used predictively), I would use the more neutral representative:

[Merriam-Webster]
1 : one that represents another or others
2 : a typical example of a group, class, or quality : SPECIMEN

From the question:

At the end of the session we see which person disagreed with others most often ("the iconoclast"), and the person who agreed with others most often ("the what?")

This could be turned into a sentence such as the following:

Her views were the most representative of our own.
She was a good representative of our group.

Or, with a variation of the word:

He best represented our views.

A related word is exemplar:

[Merriam-Webster]
: one that serves as a model or example