Is Abimelech counted among the Judges?
There are 12 judges recorded as below:
Judges 3:9 And when the children of Israel cried unto the LORD, the LORD raised up a deliverer to the children of Israel, who delivered them, even Othniel the son of Kenaz, Caleb’s younger brother. 10 And the Spirit of the LORD came upon him, and he judged Israel, and went out to war: and the LORD delivered Chushanrishathaim king of Mesopotamia into his hand; and his hand prevailed against Chushanrishathaim. 11 And the land had rest forty years. And Othniel the son of Kenaz died.
Judges 3:15 But when the children of Israel cried unto the LORD, the LORD raised them up a deliverer, Ehud the son of Gera, a Benjamite, a man lefthanded: and by him the children of Israel sent a present unto Eglon the king of Moab.
Judges 3:31 And after him was Shamgar the son of Anath, which slew of the Philistines six hundred men with an ox goad: and he also delivered Israel.
Judges 4:4 And Deborah, a prophetess, the wife of Lapidoth, she judged Israel at that time.
Judges 6:11 And there came an angel of the LORD, and sat under an oak which was in Ophrah, that pertained unto Joash the Abiezrite: and his son Gideon threshed wheat by the winepress, to hide it from the Midianites. 12 And the angel of the LORD appeared unto him, and said unto him, The LORD is with thee, thou mighty man of valour.
Judges 8:28 Thus was Midian subdued before the children of Israel, so that they lifted up their heads no more. And the country was in quietness forty years in the days of Gideon.
Judges 10:1 And after Abimelech there arose to defend Israel Tola the son of Puah, the son of Dodo, a man of Issachar; and he dwelt in Shamir in mount Ephraim. 2 And he judged Israel twenty and three years, and died, and was buried in Shamir.
Judges 10:3 And after him arose Jair, a Gileadite, and judged Israel twenty and two years. 4 And he had thirty sons that rode on thirty ass colts, and they had thirty cities, which are called Havothjair unto this day, which are in the land of Gilead. 5 And Jair died, and was buried in Camon.
Judges 11:5 And it was so, that when the children of Ammon made war against Israel, the elders of Gilead went to fetch Jephthah out of the land of Tob: 6 And they said unto Jephthah, Come, and be our captain, that we may fight with the children of Ammon.
Judges 12:7 And Jephthah judged Israel six years. Then died Jephthah the Gileadite, and was buried in one of the cities of Gilead.
Judges 12:8 And after him Ibzan of Bethlehem judged Israel. 9 And he had thirty sons, and thirty daughters, whom he sent abroad, and took in thirty daughters from abroad for his sons. And he judged Israel seven years. 10 Then died Ibzan, and was buried at Bethlehem.
Judges 12:11 And after him Elon, a Zebulonite, judged Israel; and he judged Israel ten years. 12 And Elon the Zebulonite died, and was buried in Aijalon in the country of Zebulun.
Judges 12:13 And after him Abdon the son of Hillel, a Pirathonite, judged Israel. 14 And he had forty sons and thirty nephews, that rode on threescore and ten ass colts: and he judged Israel eight years. 15 And Abdon the son of Hillel the Pirathonite died, and was buried in Pirathon in the land of Ephraim, in the mount of the Amalekites.
Judges 13:24 And the woman bare a son, and called his name Samson: and the child grew, and the LORD blessed him. 25 And the Spirit of the LORD began to move him at times in the camp of Dan between Zorah and Eshtaol.
Judges 15:20 And he judged Israel in the days of the Philistines twenty years.
Abimelech (Judges 9) is excluded, because he was not a Judge raised up by God, but a self-proclaimed king who did no good.
I hope you find this helpful.