Bitterness is a sin straight from the abyss and many are trapped in that prison of unforgiveness that has birthed bitterness in its worse form.  What does My Word tell you about bitterness?  Who walks in bitterness?  It is not a true child of the Most High God.

Why have you allowed the enemy to capture your mind and destroy you and others with his demon of bitterness.  I am coming after a bride without spot and wrinkle.  Bitterness is a blot of gross darkness on your garments and it will keep you out of the Heavenly places with Me.

Get rid of your bitterness before it consumes you.  Get it under the blood and keep it there. My Word will not be placed under anyone’s feet.  If you are calling yourself a child of God, you can have no bitterness in your mortal body.  My Word tells you to shun all manner of evil.  Bitterness is an evil.

Ephesians 4:31-32 (ESV)
31 Let all bitterness and wrath and anger and clamor and slander be put away from you, along with all malice.
32 Be kind to one another, tenderhearted, forgiving one another, as God in Christ forgave you.

Hebrews 12:15 (ESV)
15 See to it that no one fails to obtain the grace of God; that no “root of bitterness” springs up and causes trouble, and by it many become defiled;

Romans 12:17-21 (ESV)
17 Repay no one evil for evil, but give thought to do what is honorable in the sight of all.
18 If possible, so far as it depends on you, live peaceably with all.
19 Beloved, never avenge yourselves, but leave it to the wrath of God, for it is written, “Vengeance is mine, I will repay, says the Lord.”
20 To the contrary, “if your enemy is hungry, feed him; if he is thirsty, give him something to drink; for by so doing you will heap burning coals on his head.”
21 Do not be overcome by evil, but overcome evil with good.