Just a very nice article from Chabad about a man wondering if he should, or if he must say Kaddish (the mourner's prayer) over a father that abandoned him.
It's very good, and goes to the point made in the Ten Commandments that you are commanded to honour your parents-not love them. G-d doesn't command us to love them, but honour them. It's a very important point.
And, honouring your parents comes before 'thou shalt not murder' (and it's not "kill" it's murder-also a very important distinction, frequently and purposely mistranslated from Hebrew into other languages).