Thorn (verb)

To cause trouble or difficulty.

Origin:

Old english þornian, of germanic origin; related to old norse þorna "to be painful".

Examples:

1. His careless attitude is always thorn in my side.
2. The lack of proper funding was a thorn in the project's development.
3. The constant delays were thorns in the company's progress.
4. His difficult behavior was a thorn in the team's productivity.
5. His constant criticism was a thorn in my confidence.