Many languages distinguish between inclusive and exclusive first-person plural pronouns (“we”). (Click or tap here to see more details)
The inclusive “we” specifically includes the addressee (“you and I and possibly others”), while the exclusive “we” specifically excludes the addressee (“he/she/they and I, but not you”). This grammatical distinction is called “clusivity.” While Semitic languages such as Hebrew or most Indo-European languages such as Greek or English do not make that distinction, translators of languages with that distinction have to make a choice every time they encounter “we” or a form thereof (in English: “we,” “our,” or “us”).
For this verse, translators typically select the exclusive form (excluding the addressee) for the first occurrence of the pronoun (“us and you”) and either the inclusive or exclusive form for the second (“anointed us”) to either include the Corinthians or not.
The Copainalá Zoque translators chose an inclusive form for the second occurrence (“anointed us”), because they take it “as referring to Paul, his associates, and those addressed, the Corinthians, and all true Christians, if need be.” The Tok Pisin Translation uses the exclusive form for the second occurrence.
Sources: Roy and Margaret Harrison in Notes on Translation with Drills, p. 173ff. and SIL International Translation Department (1999).