The mitzva to remember the lasting damage caused by Amalek, and our hope that what they did will one day be reversed, occurs in several places in our tefilla, but one might daven his whole life and not realize what he is saying.
The passuk says ויאמר כי יד על כס י-ה מלחמה לד' בעמלק מדר דר
A reference in Kaddish:
From Sefer HaPardes/Rashi:
Tosfos Brachos 3a brings a corollary thought from the Machzor Vitri (written by Rav Simcha of Vitri, a pupil of Rashi) which explains that the congregational response to Yisgadal in kaddish, Yehei Shmei Rabba, is also a reference to this mitzva:
--A reference at the end of Davening: (guest emendation)
This is also reflected directly in the pasuk we say at the end of Aleinu- ביום ההוא יהיה ה' אחד ושמו אחד: i.e., on the day when the הוא is restored and the Name of Hashem is complete. On a deeper level, see the sugya Pesachim 50a on " אטו האידנא לאו אחד הוא ?" Note carefully the reference in that gemara to וזה זכרי לדר דר and the obvious connection to the parasha of Amalek --