Benaiah killed a lion. 2 Samuel 23
20 Benaiah son of Jehoiada, a valiant fighter from Kabzeel, performed great exploits. He struck down Moab’s two mightiest warriors. He also went down into a pit on a snowy day and killed a lion. 21And he struck down a huge Egyptian. Although the Egyptian had a spear in his hand, Benaiah went against him with a club. He snatched the spear from the Egyptian’s hand and killed him with his own spear. 22Such were the exploits of Benaiah son of Jehoiada; he too was as famous as the three mighty warriors. 23He was held in greater honor than any of the Thirty, but he was not included among the Three. And David put him in charge of his bodyguard. Why did he hesitate to kill Joab?
Out of respect for the sacred altar, he preferred to kill Joab outside of the tent.
1 Kings 2:30 So Benaiah entered the tent of the Lord and said to Joab, “The king says, ‘Come out!’ ”
But he answered, “No, I will die here.”
Benaiah then double-checked with King Solomon and killed Joab on the spot.
Was Benaiah afraid to kill Joab in the sanctuary in 1 Kings 2?
No, it wasn't fear but respect for the sacred altar.
For a job well done, the king promoted him.
1 Kings 2:34 So Benaiah son of Jehoiada went up and struck down Joab and killed him, and he was buried at his home out in the country. 35The king put Benaiah son of Jehoiada over the army in Joab’s position and replaced Abiathar with Zadok the priest.
Benaiah was a fearless might man.