John Gill Commentary 2 Samuel 16:8

"Jehovah hath returned upon thee all the blood of the house of Saul, in whose stead thou hast reigned; and Jehovah hath delivered the kingdom into the hand of Absalom thy son; and, behold, thou art [taken] in thine own mischief, because thou art a man of blood." — 2 Samuel 16:8 (ASV)

The Lord has returned upon you all the blood of the house of
Saul ;
Which he would suggest was shed by David, or, however, that he was the cause of its being shed; as if he had stirred up the Philistines to that battle in which Saul and his sons were slain, and had an hand secretly in the deaths of Ishbosheth and Abner, all which were false insinuations; and it may be the seven sons of Saul before this time, though after related, were delivered into the hands of the Gibeonites to be hanged, to which respect may be had:

in whose stead you have reigned ;
not by right, but by usurpation he suggests:

and the Lord has delivered the kingdom into the hand of Absalom your
son ;
in this he seems to contradict himself; for if David had got the kingdom by usurpation, it would rather have, been delivered by the Lord into the hand of one of Saul's family, and not of David's:

and behold, you [are taken] in your mischief ;
punished for his sins; the mischief he had brought on others was retaliated to him:

because you [are] a bloody man ;
guilty of slaying, as the Targum of shedding innocent blood, and so worthy of death.