From where do assassins originate? For some reason, after recent current events, that was my first thought. A Google® search brings up a plethora of information, a lot of which dates their origin in the 11th Century. The McClintock and Strong Biblical Cyclopedia explains assassins like this, https://www.biblicalcyclopedia.com/A/assassins.html.
Throughout my research on this topic, a common characteristic of an assassin is that they are politically motivated; they can also be religiously motivated. Whether a target through military maneuver or a lone individual, the outcome of the assassination is to change the trajectory of politics, faith and/or both politics and faith.
But even before the 11th Century, there were assassinations detailed in Scripture, especially in the upheaval of the book of Judges. Judges shows in great detail the cycle of our fallen nature and the faithfulness of our One True God.

After the deaths of Joshua and the elders under his leadership, the Israelites were being tested by the Lord. They were a young generation who did not remain faithful to God. Some tribes had successes, but most failed miserably in following the Lord’s commandments and instructions. The nations that God did not hand over to Joshua were “nations the LORD left in order to test all those in Israel who had experienced none of the wars in Cannon.” (Judges 3:1.)
One of those nations was Moab. The Moabites originated from Lot and the indiscretion of his first-born daughter (Genesis 19:30-38). In Judges, Chapter 3, Scripture tells us that, “The Israelites served King Eglon of Moab eighteen years.” (Judges 3:14.) When they finally cried out to the Lord, He raised up a man named Ehud, who was a left-handed Benjaminite (Judges 3:15). Ehud being left-handed was an advantage, and here’s why https://www.gotquestions.org/Bible-left-handed.html.

Ehud’s story is read with a plot a lot like one of our modern-day assassin movies. He was sent to King Eglon with a tribute. He also had an eighteen-inch double-edged sword strapped to his right thigh which was hidden under his clothes. Clearly, the tribute was a ruse. Once Ehud strategically got his alone time with King Eglon, he said:

“I have a message from God for you,”

“Ehud reached with his left hand, took the sword from his
right thigh, and plunged it into Eglon’s belly.”

Judges 3:20; 21 – CSB

Ehud escaped, the Israelites followed his lead into battle with the Moabites and conquered them, and “Moab became subject to Israel that day, and the land had peace for eighty years.” (Judges 3:30.)

Approximately one-hundred-and-twenty years later, this happened:

“But Sisera fled away on foot to the tent of Jael, the wife of
 Heber the Kenite, for there was peace between Jabin the
king of Hazor and the house of Heber the Kenite.”

“And he said to her, “Stand at the opening of the tent, and if
any man comes and asks you, ‘Is anyone here?’ say, ‘No.’”
But Jael the wife of Heber took a tent peg, and took a hammer
in her hand. Then she went softly to him and drove the peg
into the ground while he was lying fast asleep from weariness.
So he died.”

Judges 4:17; 20-21 – CSB

Jael is one of my favorite biblical heroes. During her lifetime, the Israelites had once again done evil in the sight of the Lord. By God’s judgment, they were handed over to the Canaanites, whose king, King Jabin, oppressed them for twenty years. Sisera was the commander of King Jabin’s army. When the Israelites finally cried out to God for help, Jael and the prophetess Deborah were used in service to God to help subdue the Canaanites. (Judges Chapters 4-5).
Jael was a female assassin.

Abimelech became king of Shechem, https://www.gotquestions.org/Shechem-in-the-Bible.html, after killing seventy of his father’s brothers – all the brothers but one, Jotham survived because he hid (Judges 9:5). Jotham then pronounced a curse on Abimelech that came to pass (Judges 9:7-15).

“When Abimelech came to attack the tower, he approached its
entrance to set it on fire. But a woman threw the upper portion
of a millstone on Abimelech’s head and fractured his skull. He
quickly called his armor-bearer and said to him, “Draw your
sword and kill me, or they’ll say about me, ‘A woman killed him.’”
So his armor-bearer ran him through, and he died.”

“In this way, God brought back Abimelech’s evil–the evil that
Abimelech had done to his father when he killed his seventy
brothers. God also brought back to the men of Shechem all their
evil. So the curse of Jotham son of Jerubbaal came upon them.”

Judges 9:52-54; 56-57 – CSB

The Bible details more instances of assassinations, but through careful study, we’ll see that such murders are not carried out for just any reason – they are God centered.
There were also assassination attempts that failed, because the failure was God centered. Saul tried to kill David for many years, on many different occasions (1 Samuel). And there were times when David could have taken Saul’s life (1 Samuel 24-31), but David was a God-fearing man, and as he states:

“May the LORD judge between me and you, and may the LORD take
vengeance on you for me, but my hand will never be against you.
 As the old proverb says, ‘Wickedness comes from wicked people.’
My hand will never be against you.”

1 Samuel 24:12-13

The rolling boil of politics and religion will ensue until who knows what is next to come. And sometimes we Christians have to get our hands dirty. A quote from Dietrich Bonhoeffer comes to mind, https://www.gotquestions.org/Dietrich-Bonhoeffer.html.

“If I sit next to a madman as he drives a car into a group of innocent
bystanders, I can’t, as a Christian, simply wait for the catastrophe,
then comfort the wounded and bury the dead. I must try to wrestle the
steering wheel out of the hands of the driver.”

https://www.azquotes.com/author/1638-Dietrich_Bonhoeffer