“לתקן עולם במלכות שדי”.
See the article on “the Seforim blog” right here by Mitchell First entitled “Le-Tacen Olam (לתכן עולם): Establishing the Correct Text in Aleinu”. (It originally appeared here.) The title is self-explanatory; the claim is made that the original and correct version of “Letaken” in “Aleinu” is spelled with the letter ‘Kaf’, not ‘Kuf’.
All I could come up with were several absent-minded interjections, like “Why not ‘Leconen’ instead?”, and “Is ‘Social Justice’ the accurate translation for ‘Tikkun Olam’?”). Instead of forming any sustained opinion on the issue, I will let you see it through virgin, unbiased eyes for yourself.
Please note: One really must check out many of the endnotes to get a decent picture of the views expressed. Indeed, this almost seems a misguided style requirement. Posts on the Seforim Blog often have footnotes more voluminous than the body of the article itself, simply because the content and citations are divided up between the two sections. What the ratio or criteria are I do not know.
(I am not saying this is more than a formal mess; I manage to read most notes without even checking what they refer to…)