And then I think "The avengers are over hyped". Those son's of Zeruiah were the real Avengers in the real sense.

Joab was one of three brothers. His brothers were Abishai who was the oldest, and Asahel the youngest. Their mother was Zeruiah, the sister of David (1 Chronicles. 2:16). So they were David’s nephews, family, sons of his sister. When David was forced to run for his life from King Saul, he found a stronghold, where he could hide.

On the one hand, these sons of Zeruiah were of great importance for David and the kingdom of Israel.
Abishai at one time killed three hundred men with a spear and he was chief of the thirty, men known for their valour.
Joab was the commander in chief of the army. Asahel was the youngest, the Bible said the guy could outrun a chariot with just his legs, How can someone be that fast!? That's faster than Usain Bolt!

David's mighty men weren't ordinary guys,They were mutants, lol or superheroes.
One of them even told David not to follow them to war again, They said he's now King, and that they're more than capable to destroy cities just for him. Those men were something else. 2 Sam 21:15-17.

On the other hand, there were times when their actions caused David to indicate his disapproval of them. After Joab treacherously killed Abner, David cried out, “And today, though I am the anointed king, I am weak, and these sons of Zeruiah are too strong for me” (2 Samuel 3:39).