Which principle do developers find most difficult to adhere to?

One of the principles of development that is often considered the most difficult to adhere to is the Single Responsibility Principle (SRP). It requires that each class or module has only one reason to change, meaning it is responsible for a single specific task.

In practice, it is challenging to correctly divide functionality, especially in large projects where responsibility boundaries can be blurred. Not following SRP leads to complex, hard-to-maintain code, where changes in one part can unexpectedly affect others.

Example: a class that is responsible for both data processing logic and interface display violates SRP. It is better to separate these responsibilities into different classes.