In my annual report every year, we list the top 10 or 20 institutions. Most of the time, it's the same ones: IRCC, CBSA, RCMP, CRA, PCO and Library and Archives. The number of complaints are usually at the highest. Whether or not they are well founded is a different subject.
I can tell you that IRCC is definitely having a hard time responding to 120,000 access requests from clients who are trying to figure out the status of their immigration or refugee file. That was what led me to do a systematic investigation last year. I did a special report on IRCC and came up with a number of recommendations. Increasing the information they provide to their clients will definitely diminish the number of access requests and complaints, as a result.