y not said: ‘Here I am reminded of the instance where Angulimala had killed a thousand people, yet still attained Arahanthood.’
Although Angulimala had killed a thousand people, yet even that was in no way as potent as an anantariya kamma. Buddha himself personally travelled to stop Angulimala from killing his mother which is an anantariya kamma. If Buddha had not intervened in a timely manner, I think Angulimala would most probably not be able to attain arahanthood after killing his mother, as his mind would be too agitated to realize the fruit and path of arahanthood, and he would be destined for niraya (though out of compassion for those who have committed anantariya akusala kamma in this life, I very much hope that they can do something to lessen any negative results).
So potent is the effect of anantariya kamma that we need to find out as much about it as we can, in my opinion.