Contradiction with Amos 3:7
Amos 3:7 suggests that God reveals His secrets to His prophets, which does not directly contradict Ezekiel 28:21 as it involves a command to prophesy.
Amos 3:7: Surely the Lord GOD will do nothing, but he revealeth his secret unto his servants the prophets.
Contradiction with Isaiah 14:12-15
This passage describes the fall of Lucifer, which is sometimes aligned with the king of Tyre's fate in Ezekiel 28 but is a different narrative.
Isaiah 14:12-15: How art thou fallen from heaven, O Lucifer, son of the morning! [how] art thou cut down to the ground, which didst weaken the nations! [O Lucifer: or, O day star]
Contradiction with Ezekiel 18:20
Talks about individual responsibility for sin, while Ezekiel 28:21 focuses on a nation (Sidon).
Ezekiel 18:20: The soul that sinneth, it shall die. The son shall not bear the iniquity of the father, neither shall the father bear the iniquity of the son: the righteousness of the righteous shall be upon him, and the wickedness of the wicked shall be upon him.
Contradiction with Jeremiah 29:11
Promises a hopeful future for people, while Ezekiel 28:21 is a warning of impending judgment.
Jeremiah 29:11: For I know the thoughts that I think toward you, saith the LORD, thoughts of peace, and not of evil, to give you an expected end. [expected...: Heb. end and expectation]