What is a figure of speech used in the first stanza of "A Poison Tree"?

A figure of speech is any use of language that goes beyond the literal to create an effect. It can include repetition, alliteration, word reversals, or any device that adds to the basic factual meaning of the words.
There are several figures of speech in the first stanza of Blake's poem. For instance, Blake employs anaphora, which is the use of the same word to begin different lines in a poem. In the first stanza, Blake repeats the word "I" at the start of each line:


I was angry with my friend;
I told my wrath, my wrath did end.
I was angry with my foe:
I told it not, my wrath did grow.


The poem also uses the reversal of standard word order in the last line. Instead of stating "I did not tell it," the speaker says "I told it not," which puts the emphasis on the "not," highlighting the negativity the speaker shows in withholding information from his enemy.
Although Blake uses simple language in this opening stanza, he also slides in figures of speech.
https://examples.yourdictionary.com/figure-of-speech-examples.html

https://www.poetryfoundation.org/poems/45952/a-poison-tree