Show Users As List Of Two, Not Frequent Posters

Ahh,

You would do something like

/* hide all avatars */
.topic-list .posters a {
    display: none;
}

/* display first avatar in list */
.topic-list .posters a:first-of-type {
    display: inherit;
}

/* display avatar of latest */
.topic-list .posters .latest {
    display: inherit;
}

Not a:last-of-type cause it could target frequent.