Messiah

キリスト (transliteration of ‘Christos’) is the standard term — so standard that ‘Christianity’ itself is キリスト教. The risk here is not syncretism but biblical illiteracy: most secular Japanese know ‘Kirisuto’ only as a foreign cultural reference point (commercialized Christmas, Western-style wedding-chapel aesthetics chosen for style rather than belief) with no connection to the Old Testament messianic-fulfillment concept the term actually carries. Heavy explanatory teaching is required, not just correct word choice.