At the gate of hell, dante sees this inscription that he calls “hard to take.” how does the use of anaphoric affect the impact of the inscription

We refer to Anaphora as a literary device that employs repetition of a certain phrase throughout several lines, right at the beginning of each. This is one of the oldest resources of speech that serve to put major emphasis on a certain idea we want to get across with particular strength and a sense of dramatism. We even use it in everyday life more than we might be aware of.

Anyhow, going back to specifics about Dante's writing in this piece, we can see very clearly how he exploits this device:

"Through me pass into the painful city, / Through me pass into eternal grief, / Through me pass among the lost people... / Before me nothing was created that / Was not eternal, and I last eternally. / All hope abandon, you who enter here."

Here, Dante is using the anaphora as part of a very poignant warning to all who are faced by the gate of hell: anyone must pass through him first, before eternal grief commences.

Hope this helps!