CREATE TABLE table_44042 ("Res." TEXT, "Record" TEXT, "Opponent" TEXT, "Method" TEXT, "Event" TEXT, "Round" FLOAT, "Time" TEXT)

What opponent used the Ko method, and a 6-0 record?
SELECT "Opponent" FROM table_44042 WHERE "Method" = 'ko' AND "Record" = '6-0'
SELECT "Opponent" FROM "table_44042" WHERE "Method" = 'ko' AND "Record" = '6-0'