I did some digging to refresh my memory and there's no way I can give a comprehensive account of all of the details, but for a few examples:
Downplaying of Jesus's miracles in:
John 5:4, Luke 8:42-45, John 11:41, Mark 1:31, Mark 3:14-15, and many others.
An interesting verse comparison:
1 Corinthians 6:9 (KJV) Know ye not that the unrighteous shall not inherit the kingdom of God? Be not deceived: neither fornicators, nor idolaters, nor adulterers, nor effeminate, nor abusers of themselves with mankind,
1 Corinthians 6:9 (NIV) Or do you not know that wrongdoers will not inherit the kingdom of God? Do not be deceived: Neither the sexually immoral nor idolaters nor adulterers nor men who have sex with men
KJV: Woe unto you, scribes and Pharisees, hypocrites! for ye devour widows' houses, and for a pretence make long prayer: therefore ye shall receive the greater damnation.
Matthew:23:14
NIV: (missing)
The more I look, there are tons of missing verses in the NIV.
A massive list of differences
The most interesting part though is that the NIV received a couple of revisions in 2004 and 2011 respectively. What did they change?
They made everything they could
gender neutral.
This site is a pretty good place for comparing a verse between a few different versions.
I didn't even get into the changes involving the bias of the NIV publishers, but hopefully that helps give an idea.