Let's actually use the Bible to answer this!
Ideas about what was blotted out in Colossians 2:14 vary, but often people disregard how God has already used that phrase when they come up with their ideas. In this video, I look up "blot out" and "blotted out" and see how God uses this phrase in the rest of scripture before determining if any of those uses are applicable in Colossians 2:14. Hopefully this'll be some good food for thought.
What was BLOTTED OUT? - VIDEO