"I genuinely value honest feedback from coworkers. I would first thank this individual for bringing the issue to light in an authentic manner. I prefer to discuss situations like this out in the open so that they can be addressed and resolved quickly.
My next move would be to consider the details of their assessment. I would ask them to explain anything that was unclear and also ask them for an example of proper execution. I may need to rework my deliverables or spend extra time educating myself on a particular concept. I would also seek out a mentor or a coworker who thrives in this area so that I could use their work as an example of the level of quality to aim for in the future.
Once the issue has been addressed, I would circle back around with the coworker to ask for their thoughts on my latest work. It is important to me to continuously learn and demonstrate growth. I would thank them again for their candor and be prepared to do the same for other coworkers in the future."