Are there greater sins than 'adultery'? Jesus did not stone to death the woman 'caught' in adultery - just pointed out that "let the person who is withiut sin" start the execution. And He did not even go looking for the man involved in the act. Just said "sin no more". And for the Samaritan woman with adultery 5 times over, He didn't even require that.

Then there are the other Gospel passages that says "no divorce - except in case of adultery" - or even lesser sexual sin, in recent translations.

 Or St. Paul in 1 corinthians who advised divorce from a non-Christian spouse who would not live in peace,  1 Corinthians 7:15 (ESV) "But if the unbelieving partner separates, let it be so. In such cases the brother or sister is not enslaved. God has called you to peace."

The Joy of Love suggests that a prime consideration be the well-being of the children involved in a divorce or a re-marriage situation. That seems to be obvious common sense. Harming children is the greater sin.