45 Heb “an evil spirit.” A nonphysical, spirit being is in view, like the one who volunteered to deceive Ahab (1 Kgs 22:21). The traditional translation, “evil spirit,” implies the being is inherently wicked, perhaps even demonic, but this is not necessarily the case. The Hebrew adjective רָעַה (ra’ah) can have a nonethical sense, “harmful; dangerous; calamitous.” When modifying רוּחַ (ruakh, “spirit”) it may simply indicate that the being in view causes harm to the object of God’s judgment. G. F. Moore (Judges [], ) here refers to a “mischief-making spirit.”
46 Heb “The leaders of Shechem were disloyal.” The words “he made” are supplied in the translation for clarification.

In other versions

And God sent an evil spirit between Abimelech and the leaders of Shechem, and the leaders of Shechem dealt treacherously with Abimelech,

God stirred up animosity between Abimelek and the citizens of Shechem so that they acted treacherously against Abimelek.

God sent an evil spirit between Abimelech and the citizens of Shechem. They treated Abimelech deceitfully,

God sent a spirit that stirred up trouble between Abimelech and the leading citizens of Shechem, and they revolted.

And God sent an evil spirit between Abimelech and the lords of Shechem, and the lords of Shechem dealt treacherously with Abimelech,

Then God sent an evil spirit between Abimelech and the men of Shechem; and the men of Shechem dealt treacherously with Abimelech:

Public Domain