Consider Jesus words in: Matthew 20:28-29 (New International Version)
"28 just as the Son of Man did not come to be served, but to serve, and to give his life as a ransom for many."
Who gave his life for us? Answer: Jesus Christ. It was Gods plan, but Jesus could have refused to do it. It was Jesus who wanted to free us from sin and death. Imagine also all the pain he had in the last days of his earthly life. Jesus personally died for us, It was not Yahweh who did this. This was the greatest display of love a man can show. John 15: 13 " Greater love has no one than this, that he lay down his life for his friends."
Then Christians should foremost thank Jesus Christ for the ransom sacrifice. I have never heard any Jehovahs witness render gratitude directly to Jesus.