Contradiction with John 3:36
This verse suggests that eternal life is conditional on belief, whereas Colossians 1:27 speaks of Christ being in believers as an assurance of glory regardless of conditions.
John 3:36: He that believeth on the Son hath everlasting life: and he that believeth not the Son shall not see life; but the wrath of God abideth on him.
Contradiction with John 15:5
This verse states that without abiding in Christ, one can do nothing, potentially contradicting the idea of Christ already being in believers as mentioned in Colossians 1:27.
John 15:5: I am the vine, ye [are] the branches: He that abideth in me, and I in him, the same bringeth forth much fruit: for without me ye can do nothing. [without me: or, severed from me]
Contradiction with James 2:26
This verse emphasizes that faith without works is dead, potentially contradicting the guarantee of glory through Christ in you found in Colossians 1:27, if actions are required.
James 2:26: For as the body without the spirit is dead, so faith without works is dead also. [spirit: or, breath]
Contradiction with Matthew 7:21
Implies that not everyone who acknowledges Christ will enter the kingdom of heaven, which contrasts with the assurance of glory through Christ in believers as noted in Colossians 1:27.
Matthew 7:21: Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven.