David is a great warrior(no doubt), at a very young age, He killed Goliath, killed a bear and he he generally considered fearless. But, while going through the Bible, I discovered David feared Joab greatly (see 2 Sam 3:39, "these sons of Zeruiah are too strong for me") and I wondered why he had so much fear for him. An example, Joab killed Abner and Amasa and David did nothing about it and He also gave instructions that Absalom's life should be speared but Joab went against the order by killing Absalom and it also took Joab alone to get David to address the people when Absalom died.
Did he feared him because of Joab is mightier and powerful than him or because Joab had more troop than him or why did he feared him so much that Joab became lawless at times