In Al Hanissim on Purim, we praise Hashem directly
וְאַתָּה בְּרַחֲמֶיךָ הָרַבִּים. הֵפַרְתָּ אֶת עֲצָתו. וְקִלְקַלְתָּ אֶת מַחֲשַׁבְתּו. וַהֲשֵׁבותָ לּו גְּמוּלו בְּראשׁו. וְתָלוּ אותו וְאֶת בָּנָיו עַל הָעֵץ - In great mercy You frustrated his counsel and ruined his plan, and You returned his plan upon his own head and they hanged him and his sons upon the tree.
However, when thanking Him for hanging Haman and his sons, we revert to "they" rather than "You" - why?