What is chronologically the last mention of redemption in the Bible?
The last mention of the English noun 'redemption' in the English bible (I am quoting from the KJV and using the list of words compiled by Robert Young in his Analytical Concordance) is in Hebrews 9:12.
The last mention of the English verb 'redeem' in the English bible is in Revelation 14:4. John the Apostle lived (and wrote) until approximately the year 100 and was (I assume without dispute) the last to write recorded scripture. So this might be the definitive answer to your question ... but ...
There are two groups of words in Greek which are translated 'redeem' and 'redemption' in English.
The 'agora' group is based on the word relating to the place of public concourse and there are two main words agora and agorazo which feature in the bible.
The 'lutron' group is based on the word luo meaning 'to dispossess' and several words are involved - lutron, lutrosis and apolutrosis.
So it would be more complicated if you were asking about the original manuscripts in Greek ... and ... the Greek words are not consistently translated in the English bible, sometimes being translated into such words as 'purchase'.
The whole subject of redemption is an important one in the bible in both the Hebrew scriptures and the Greek scriptures. The two groups of Greek words mirror two words in Hebrew gaal (used many times in the Book of Ruth and elsewhere) and padah (never used in Ruth but used otherwise).
The question is a little more complicated to answer than it, at first, appears.