Here is some ayat :
Quran 58:22
لَا تَجِدُ قَوْمًا يُؤْمِنُونَ بِاللَّهِ وَالْيَوْمِ الْآخِرِ يُوَادُّونَ مَنْ حَادَّ اللَّهَ وَرَسُولَهُ وَلَوْ كَانُوا آبَاءَهُمْ أَوْ أَبْنَاءَهُمْ أَوْ إِخْوَانَهُمْ أَوْ عَشِيرَتَهُمْ ۚ أُولَٰئِكَ كَتَبَ فِي قُلُوبِهِمُ الْإِيمَانَ وَأَيَّدَهُمْ بِرُوحٍ مِنْهُ ۖ وَيُدْخِلُهُمْ جَنَّاتٍ تَجْرِي مِنْ تَحْتِهَا الْأَنْهَارُ خَالِدِينَ فِيهَا ۚ رَضِيَ اللَّهُ عَنْهُمْ وَرَضُوا عَنْهُ ۚ أُولَٰئِكَ حِزْبُ اللَّهِ ۚ أَلَا إِنَّ حِزْبَ اللَّهِ هُمُ الْمُفْلِحُونَ
You will not find a people who believe in Allah and the Last Day having affection for those who oppose Allah and His Messenger, even if they were their fathers or their sons or their brothers or their kindred. Those - He has decreed within their hearts faith and supported them with spirit from Him. And We will admit them to gardens beneath which rivers flow, wherein they abide eternally. Allah is pleased with them, and they are pleased with Him - those are the party of Allah . Unquestionably, the party of Allah - they are the successful.
(here what translated into fathers, in Arabic means parents)
Quran 9:23
يَا أَيُّهَا الَّذِينَ آمَنُوا لَا تَتَّخِذُوا آبَاءَكُمْ وَإِخْوَانَكُمْ أَوْلِيَاءَ إِنِ اسْتَحَبُّوا الْكُفْرَ عَلَى الْإِيمَانِ ۚ وَمَنْ يَتَوَلَّهُمْ مِنْكُمْ فَأُولَٰئِكَ هُمُ الظَّالِمُونَ
O believers! Do not take your fathers and your brothers as your friends if they prefer Kufr (unbelief) over Iman (belief); for those who turn away from this commandment shall be considered wrongdoers.
I know these are not direct answers to your question, because an abusive parent doesn't necessarily mean a disbeliever, but this is the example I could fin in Quran when it's allowed to somehow "abandon" your parents. And you could argue that a child abuser is opposing Allah and His messenger.
And Allah knows better.