diabolical

The story

1. Proto-Indo-European*dwóh₁
2. Proto-Indo-European*trísinflu.
3. Proto-Indo-European*dwís
4. Ancient Greekδιά (diá)
5. Ancient Greekδια- (dia-)
6. Proto-Indo-European*gʷelH-
7. Proto-Hellenic*gʷəlnō
8. Ancient Greekβάλλω (bállō)
9. Ancient Greekδιαβάλλω (diabállō)
10. Ancient Greekδιάβολος (diábolos)
11. Koine Greekδιαβολικός (diabolikós)
12. Late Latindiabolicu
13. Middle Frenchdiabolique
14. Middle Englishdiabolik
15. Englishdiabolic
16. Proto-Indo-European*h₂el-
17. Proto-Indo-European*h₂élisder.?
18. English todaydiabolical

From diabolic + -al.