Can someone do mighty miracles in the name of Jesus and fail to be saved?

"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. Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works? And then will I profess unto them, I never knew you: depart from me, ye that work iniquity. (Matthew 7:21-23 KJV)

What does the word "iniquity" mean?  

G458 - "Anomia" in Koine Greek

Deut 31:29; Psalm 119:150; Ezekiel 18:20-22; Lamentations 4:6

"Be ye not unequally yoked together with unbelievers: for what fellowship hath righteousness with unrighteousness? and what communion hath light with darkness?" (2 Corinthians 6:14 KJV) 

"Whosoever committeth sin transgresseth also the law: for sin is the transgression of the law." (1 John 3:4 KJV)